docs(review 002): fix unsatisfiable R-02 acceptance gate

The R-02 acceptance gate was a line-level grep
(`grep -v 'mod tests'`) that cannot return zero while any test uses
`.expect()` — `grep -v` filters per-line, not per-scope, so every
`.expect(` inside a `#[cfg(test)] mod tests {}` block whose
individual line lacks the literal "mod tests" still matches. The suite
has ~269 such test-only `expect` calls, making the literal gate
unsatisfiable (an impossible-goal spec bug, surfaced during Unit 1
remediation).

Replace both copies of the gate (the R-02 finding gate and the Unit 1
acceptance gate) with a scope-aware verification: either (a) a targeted
grep for the specific removed strings, or (b) file-by-file confirmation
that every remaining `.expect(` is within a `#[cfg(test)] mod tests`
boundary. The intent — no `expect` in library (non-test) code — is
unchanged; only the verification method is corrected.

docs/reviews/002-pre-publish-coverage-and-cleanup-review.md

@@ -140,9 +140,17 @@ blocks and are fine.
 `operations.rs:415`, use `channel_open.as_ref().ok_or_else(||
 ...)?.alpn.to_string()` to avoid the expect entirely.
 
-**Acceptance gate:** `grep -rn '\.expect(' src/ --include='*.rs' | grep
--v '#\[cfg(test)\]' | grep -v 'mod tests' | grep -v '#\[test\]' | grep
--v test_support` returns no matches.
+**Acceptance gate:** no `.expect(` in non-test library code. Verify
+scope-aware — the earlier line-level grep gate (`grep -v 'mod tests'`)
+is unsatisfiable: `grep -v` filters per-line, not per-scope, so every
+`.expect(` inside a `#[cfg(test)] mod tests {}` block whose individual
+line lacks the literal `mod tests` still matches (the suite has ~269
+such test-only `expect` calls). Use either: (a) a targeted grep for the
+removed strings — `grep -rn 'expect("checked above")\|expect("stream
+mutex poisoned")' src/` returns no matches; or (b) a scope-aware check
+(e.g. `awk` state-tracking of `mod tests` blocks, or manual
+file-by-file confirmation that every remaining `.expect(` is within a
+`#[cfg(test)] mod tests` boundary).
 
 ## R-03 [minor] — Unnecessary `#[allow(dead_code)]` on `generate_request_id`
 
@@ -461,9 +469,10 @@ code; no unnecessary `#[allow(dead_code)]`.
   - `types.rs:436,456`: use `unwrap_or_else(|e| e.into_inner())`.
 - **R-03:** remove `#[allow(dead_code)]` from `context.rs:147`.
 **Acceptance gate:** `cargo publish --dry-run --allow-dirty` succeeds;
-`grep -rn '\.expect(' src/ --include='*.rs' | grep -v '#\[cfg(test)\]'
-| grep -v 'mod tests' | grep -v '#\[test\]' | grep -v test_support`
-returns no matches; `cargo test` green; clippy/fmt/doc clean.
+no `.expect(` in non-test library code (see R-02 for the scope-aware
+verification method — do **not** use the line-level `grep -v 'mod
+tests'` gate, it is unsatisfiable); `cargo test` green; clippy/fmt/doc
+clean.
 
 ## Unit 2 — Single-stream call mode tests (R-04)