chore: verify MSRV 1.85, pin 1.85-compatible transitive deps (N6)

- cargo +1.85 check passes (default + --all-features), plus wasm
  target check and a full +1.85 test --all-features run (136 tests).
  The declared MSRV is real, not aspirational.
- the lockfile pins the 1.85-compatible transitive set (jsonschema
  0.46.9, idna_adapter 1.2.0, icu crates 2.0.x) — idna_adapter 1.2.2
  requires rustc 1.86, icu 2.3 requires 1.88; stable still resolves
  and all tests pass.
- review #001 is now fully resolved (status: fully-resolved). A CI
  MSRV job can gate on 'cargo +1.85 check' once CI exists.

docs/reviews/001-code-review.md

@@ -1,5 +1,5 @@
 ---
-status: partially-resolved (L6, N4, N6)
+status: fully-resolved
 last_updated: 2026-09-05
 reviewed_artifacts:
   - src/lib.rs
@@ -521,6 +521,9 @@ Highlights:
 
 ## Remediation Plan
 
+All findings are resolved — see the resolution sections below for
+dates and commit references.
+
 | ID | Finding | Fix | Effort | Risk | Status |
 |----|---------|-----|--------|------|--------|
 | L5 | `cargo fmt` fails | run `cargo fmt`, commit | trivial | none | ✅ resolved |
@@ -536,7 +539,7 @@ Highlights:
 | L3 | `open_via_channels` 0% covered | end-to-end channels consumer test | medium | low | ✅ resolved (2026-09-05) |
 | L6 | pty bridge error paths untested | targeted error-path tests | medium | low | ✅ resolved (2026-09-05) |
 | N4 | sleep-based timing | readiness signals | small | low | ✅ resolved (2026-09-05) |
-| N6 | MSRV unverified | CI MSRV job or bump | small | none | open |
+| N6 | MSRV unverified | CI MSRV job or bump | small | none | ✅ resolved (2026-09-05) |
 
 ### Resolution (2026-08-17, commit `9944153`)
 
@@ -677,13 +680,26 @@ whenever the control handle exists — the sleeps there were pure
 latency. Integration suites now finish in ~40 ms (was 200-270 ms
 each).
 
+### Resolution (2026-09-05, N6 — MSRV verified at 1.85)
+
+`cargo +1.85 check` passes for the default crate and `--all-features`,
+plus `cargo +1.85 check --target wasm32-unknown-unknown` and a full
+`cargo +1.85 test --all-features` (all 136 tests). The declared MSRV
+1.85 is real.
+
+The only friction was transitive: `idna_adapter@1.2.2` (via
+`idna` ← `jsonschema` ← alkcall) requires rustc 1.86, and the icu
+v2.3 crates require 1.88. The Cargo.lock now pins the 1.85-compatible
+set (`jsonschema 0.46.9`, `idna_adapter 1.2.0`, icu crates at 2.0.x)
+— verified on stable too. If a future dependency bump silently raises
+the real MSRV, `cargo +1.85 check` in CI will catch it (the toolchain
+is installed via `rustup toolchain install 1.85 --profile minimal` +
+`rustup target add wasm32-unknown-unknown --toolchain 1.85`; no CI
+job exists yet, so the command here is the check until one does).
+
 ### Remaining (open)
 
-- **N6** — MSRV unverified.
-
-### Recommended Order (remaining)
-
-1. **N6** — MSRV; defer until CI exists.
+None — the review is fully resolved.
 
 ---