docs: address Codex review of the RFC reorg

- Fix two root-AGENTS.md cross-links that the depth bump left pointing at the
  new docs/AGENTS.md instead of the root file they cite (capability-seams,
  optional-code-mode). These resolved on disk so verify-md-links passed — the
  gate checks existence, not which file you meant; corrected to ../../../.
- Broaden verify-md-links scope to .agents/skills/**/*.md: this PR rewrote the
  dsh-code-review skill's links into the RFC tree, but the skill dir was outside
  the gate, so a broken skill link would have passed silently.
- Percent-decode the path component before the existence check, so a valid
  encoded relative target (My%20File.md) is not falsely reported broken; a
  malformed escape (%zz) is reported broken rather than crashing the gate.
- Drop the merged property-testing RFC's "nightly CI job 100x" claim: that line
  came from the original proposal, not the accepted decision, and CI has only
  push/pull_request triggers — note it as possible future work instead.

doc-sync (incl. verify-md-links over 58 files), doc-typecheck, lint pass.

docs/rfc/implemented/2026-06-11-property-based-testing.md

@@ -12,7 +12,7 @@ Example-based tests pin the cases we thought of. The harness's core is protocol-
 
 ## Decision
 
-Adopt `fast-check` (a root devDependency) with one `tests/properties.spec.ts` per protocol-shaped package, generators tuned for *realistic-but-adversarial* inputs (not uniform noise) and `numRuns` kept so the suite stays well under ~10s locally, with a nightly CI job running 100× the iterations. Failures print a reproducible seed.
+Adopt `fast-check` (a root devDependency) with one `tests/properties.spec.ts` per protocol-shaped package, generators tuned for *realistic-but-adversarial* inputs (not uniform noise) and `numRuns` kept so the suite stays well under ~10s locally. Failures print a reproducible seed. (The original proposal also sketched a nightly CI job running 100× the iterations; that was not shipped — the property suite runs only in the normal `push`/`pull_request` CI, and a scheduled high-iteration job remains possible future work.)
 
 - **dsh-llm / BlockAssembler:** arbitrary chunk streams (valid + malformed: duplicate indices, stragglers, missing block-start). Invariants: `flushReady()+flushRemaining() ≡ blocks()` in order; the streamed prefix is always a prefix of final `blocks()`; partial count ≤ distinct indices; re-assembly idempotent.
 - **dsh-session:** arbitrary event logs. Invariants: `deriveMessages` deterministic; replay-from-seed identical; seq strictly monotonic; non-message events never affect derived history; derived content is decoupled from the log.