docs(agents): detect silently-fixed issues and link fixes to issues at merge

triage-issues gains a silently-fixed detection ladder, strongest
evidence first: mechanism-anchor (git log -L on the root-cause:found
file:line since the issue date), repro re-run against current main, and
symptom search over commits/CHANGELOG/merged PR titles. CLOSE-FIXED
always names its evidence; an unverified hunch only asks the reporter
to retry.

pr-review's merge verdicts now search open issues for the symptom a bug
fix resolves and propose Closes #N, so fixes stop landing unlinked.

.agents/skills/pr-review/SKILL.md

@@ -33,6 +33,8 @@ Choose exactly one. When torn between two, the deciding question is always: **wh
 
 4. **MERGE** — nothing to fix. Ready action: merge with a short genuine thank-you.
 
+**Link the issues a fix closes.** For every MERGE and MERGE-THEN-FIX verdict on a bug fix, search open issues for the symptom the PR resolves (`gh issue list --search` with the error strings and area terms) — contributors often fix problems without linking them. Any match goes into the ready action as a proposed "Closes #N" / close-on-merge so fixed issues never linger open unlinked.
+
 Manual verification the agent cannot perform (device testing, packaged builds, visual states) does not create a fifth verdict: pick the verdict the code earns and attach a **"needs your hands"** line saying exactly what to check and what outcome confirms it.
 
 ## Process