re-baseline the four pending remediation tasks against the ADR-007/008 tree

The tasks were decomposed (d7db6b1) before 49d4432/ac440f3 landed;
both commits touched exactly the areas the tasks reference. Fixes
grounded in verified sources (vendored rustls-acme 0.12.1, rustls-pemfile
2.2.0, rustls-native-certs 0.8.4) and a fresh cargo llvm-cov run:

- acme-event-loop-test: the termination assertion was impossible —
  rustls-acme's Stream for AcmeState never yields None
  (state.rs:407-412, poll_next_infinite + 2^16s backoff); the review's
  U-1 exit-condition premise is withdrawn and corrected in place.
  Replaced with timeout-bounded event collection, a reachable-arm
  inventory (Order warn, AccountCacheStore, Load/Parse error arms,
  DeployedCachedCert/CertCacheStore via deterministic DirCache file
  pre-seeding), and an explicit mark for the full-fake-CA arms.
  server.rs:135 flagged as unreachable dead code (delete or accept).
- coverage-cheap-closes: re-baselined per-line ground truth — original
  groups 1 and 5 are already closed by the handshake suites; group 2's
  TLS 1.3 half is covered, leaving the TLS 1.2 else-arm (client.rs:316);
  new group added for VerifyPresentedCertVerifier::verify_tls12_signature
  (server.rs:349-366, opened by ADR-008; required for the >=98% bar);
  AcceptAnyCertVerifier refs moved to server.rs:468-475 with the stale
  OQ-TLS-09 coordination caveat retired.
- docs-pin-c1-c4-n3-n4: N-4 re-scoped (the mechanism analysis already
  lives in ADR-007 + the resolver doc block; what remains is a short
  server-verifier note covering both verifiers); C-4 updated for
  ADR-007's negotiation-earlier failure point; added the
  FingerprintPinVerifier pop cross-ref update (post-ADR-008 the default
  verifier does verify possession).
- config-validation-and-trivia: added the feature-gate mechanics note
  for the C-3 test (a non-gated test passes vacuously under default
  features); refreshed drifted line refs with a re-grep advisory.
- review 001: Status block records OQ-TLS-09/-10 resolutions; U-1
  carries the termination correction; U-2 carries the supersession
  note. ADR-008 gains the suite-number-to-test-name mapping.

Verification: taskgraph validate 14 tasks; cargo doc --no-deps
warning-free; all edits docs-only (no code paths touched).

tasks/coverage-cheap-closes.md

@@ -1,6 +1,6 @@
 ---
 id: coverage-cheap-closes
-name: Cheap coverage closes — resolver resolve() calls, non-Ed25519 pin arm, PEM parse-error arm, fallback seam (U-2)
+name: Cheap coverage closes — non-Ed25519 pin arms, PEM parse-error arm, fallback seam, escape-hatch methods (U-2, re-baselined)
 status: pending
 depends_on: []
 scope: narrow
@@ -12,56 +12,84 @@ tags: [tests, coverage, review-001, u2]
 
 ## Description
 
-The coverage inventory (review 001 Part C, re-verified in the
-decomposition session — llvm-cov matches every listed range) shows
-several small, cheap-to-close gaps. One pass over unit + integration
-tests closes them all. Per group:
+The coverage inventory (review 001 Part C) — **re-baselined
+2026-09-12 by a fresh `cargo llvm-cov --all-features` run** after
+ADR-007/ADR-008 landed (commits `49d4432`/`ac440f3`): the new
+handshake and impersonation suites already closed two of the original
+groups, and ADR-008's new verifier opened one new gap. Current
+per-line ground truth (all line numbers re-verified against the
+current tree):
 
-1. **client.rs 183-189, 212-218** — `RawKeyClientCertResolver::resolve`
-   and `NoClientCertResolver::resolve` are never *called* by a test.
-   One-line tests: `resolve` returns `Some(key)` for the raw-key
-   resolver and `None` for `NoClientCertResolver`.
-2. **client.rs 297, 316-322** — `FingerprintPinVerifier`'s
-   non-Ed25519 TLS 1.3 signature arm
-   (`rustls::crypto::verify_tls13_signature`) is only covered by the
-   deleted review probes. Pinned test: an ECDSA-P256 rcgen cert +
-   `dss_with_scheme` (P256/SHA256), assert ok, then a forged sig →
-   err. Mirrors the existing Ed25519 routing pin
-   (`fingerprint_pin_verifier_routes_ed25519_spki_tls13_signature_through_raw_key_path`).
-3. **pem.rs 30** — the `Err(e) => Err(io::Error::other(e))` arm of
+1. **client.rs:316** — `FingerprintPinVerifier::
+   verify_tls12_signature`'s non-Ed25519 else-arm
+   (`rustls::crypto::verify_tls12_signature`) is never executed. (The
+   original group-2 text pointed at the TLS 1.3 twin at 297/316-322 —
+   that TLS 1.3 arm is now covered by the handshake suite's pin
+   suites; only the TLS 1.2 else-arm remains.) Pinned test: an
+   ECDSA-P256 rcgen cert + `dss_with_scheme` (P256/SHA256) against
+   `verify_tls12_signature`, assert ok, then a forged sig → err.
+   Mirrors the existing Ed25519 TLS 1.3 routing pin
+   (`fingerprint_pin_verifier_routes_ed25519_spki_tls13_signature_
+   through_raw_key_path`, client.rs:472).
+2. **server.rs:349-366** — `VerifyPresentedCertVerifier::
+   verify_tls12_signature`'s body (ADR-008's default verifier; did
+   not exist at decomposition time) is entirely uncovered: no TLS 1.2
+   handshake exists in the suite. Same pop-routing shape as the pin
+   verifier (Ed25519-SPKI → `verify_tls13_signature_with_raw_key`,
+   else `verify_tls12_signature`). A direct unit-call test (Ed25519
+   SPKI + valid sig → ok; wrong-key or mismatched-message dss → err)
+   closes it. **This group must be included or the ≥98% acceptance
+   bar is unreachable while the ACME loop stays open** (owned by
+   `acme-event-loop-test`).
+3. **pem.rs:30** — the `Err(e) => Err(io::Error::other(e))` arm of
    `load_private_key` (a *parse* failure, distinct from "no key
    found") has no test: garbage-but-keyed file
    (`b"-----BEGIN PRIVATE KEY-----\n!!!\n-----END PRIVATE KEY-----\n"`)
-   exercises it.
-4. **client.rs 144-147** — the webpki-roots fallback *push* loop is
+   exercises it. Verified against rustls-pemfile 2.2.0: malformed
+   base64 in a keyed section is a real `Error::Base64Decoding`-class
+   `Err` from `private_key` — the prescribed input works.
+4. **client.rs:145-148** — the webpki-roots fallback *push* loop is
    covered only nondeterministically (passes vacuously when the
    platform store is non-empty). Deterministic remediation: a
    `#[cfg(test)]`-visible helper taking the "native certs" as a
    parameter (or an injectable `load_native_certs` seam) so the
    empty-platform case is testable without root. This is a
    load-bearing invariant whose fallback branch has no deterministic
-   test.
-5. **server.rs 341-346** — `RawKeyCertResolver::resolve` is never
-   called (only `only_raw_public_keys()` is). A one-line assert
-   (`resolve(hello).is_some()`) covers it — a `ClientHello` can be
-   synthesized via `rustls::server::test_client_hello`-style helpers;
-   the end-to-end raw-key handshake in `handshake-tests` also covers
-   it, but the one-liner keeps this task independent of that one.
-6. **server.rs 287-303** — `AcceptAnyCertVerifier`'s two
-   signature-assertion methods are never called by a test. Two-line
-   test each (call, assert `Ok`), making the no-pop posture explicit
-   in the suite. Note: this pins the *current* behavior; if
-   OQ-TLS-09's resolution changes the verifier, these tests change
-   with it (coordinate with `fix-accept-any-cert-verifier-posture`).
-7. **fingerprint.rs 67** — the second disjunct
+   test. (`rustls_native_certs::CertificateResult` has public `certs`
+   / `errors` fields, so the seam shape is a plain refactor — see
+   Work item 2.) The `tracing::warn!` for native-cert errors at
+   client.rs:139 sits in the same uncovered pocket.
+5. **server.rs:468-475** — `AcceptAnyCertVerifier` (now the
+   *escape-hatch* verifier post-ADR-008, moved to server.rs:429) is
+   only partially covered by the impersonation suite's escape-hatch
+   tests: `verify_tls12_signature`'s body and
+   `supported_verify_schemes()` (468-475) are never called. Two-line
+   test each (call, assert `Ok` / assert the nine-scheme list),
+   making the no-pop posture explicit in the suite. (The original
+   group-6 range 287-303 is now `VerifyPresentedCertVerifier`'s code
+   — the file shifted under the ADR-008 commit.) Note: the original
+   "coordinate with OQ-TLS-09's resolution" caveat is stale —
+   OQ-TLS-09 is resolved (ADR-008), the escape-hatch posture is
+   permanent and pinned by `tests/impersonation_posture.rs`.
+6. **fingerprint.rs:67** — the second disjunct
    (`len() != 33 || [0] != 0x00`) matrix case (34-byte bit-string +
    unused-bits ≠ 0 vs len ≠ 33). Cosmetic.
 
+**Already closed by the ADR-007/ADR-008 suites (do not redo):** the
+client resolvers' `resolve` calls (original group 1 —
+`RawKeyClientCertResolver::resolve` and `NoClientCertResolver::resolve`
+are exercised by the handshake suites) and `RawKeyCertResolver::resolve`
+(original group 5 — exercised end-to-end by
+`tests/handshake_behavior.rs`, e.g.
+`raw_key_client_presents_spki_and_server_extracts_fingerprint`).
+`FingerprintPinVerifier::verify_tls13_signature`'s non-Ed25519 arm
+(original group 2's TLS 1.3 half) is also covered.
+
 ## Work
 
 1. Write the unit tests (in-module `#[cfg(test)]` where the items are
    private-visible, tests/ where public API suffices).
-2. Group (4) is the only one touching non-test code: extract a
+2. Item 4 is the only one touching non-test code: extract a
    test-visible seam for the fallback loop. Keep the seam
    `#[cfg(test)]`-visible or behind a plain `pub(crate)` fn — do not
    grow the public API.
@@ -69,24 +97,28 @@ tests closes them all. Per group:
 
 ## Verification
 
-- [ ] `cargo llvm-cov --all-features` shows the seven groups covered
-      (client.rs 183-189/212-218/297/316-322, pem.rs 30, server.rs
-      287-303/341-346, fingerprint.rs 67)
+- [ ] `cargo llvm-cov --all-features` shows the six groups covered
+      (client.rs 316/145-148, pem.rs 30, server.rs 349-366/468-475,
+      fingerprint.rs 67)
 - [ ] The fallback test deterministically exercises the push loop
       (platform-store-independent)
 - [ ] `cargo test`, `cargo test --all-features`, clippy, fmt green
 
 ## Acceptance Criteria
 
-- [ ] Line coverage ≥ 98% (from 95.32%) with every load-bearing
-      uncovered group closed
+- [ ] Line coverage ≥ 98% (from 95.81% currently; 95.32% at
+      decomposition) with every load-bearing uncovered group closed
 - [ ] No public-API growth
 
 ## References
 
-- docs/reviews/001-implementation-review.md §U-2, Part C (the inventory)
+- docs/reviews/001-implementation-review.md §U-2, Part C (the
+  inventory rows for the closed groups are stale — this task's
+  Description is the current baseline)
 - src/client.rs, src/pem.rs, src/server.rs, src/fingerprint.rs
-- tasks/handshake-tests.md (the overlap note for group 5)
+- tests/handshake_behavior.rs (the suites that closed original groups
+  1 and 5), tests/impersonation_posture.rs (the escape-hatch pins —
+  group 5's `verify_tls13_signature` coverage comes from here)
 
 ## Notes