fix: re-anchor doc citations that the CONTEXT.md trim broke

Why: eight comments and one status note cited CONTEXT.md or AGENTS.md text that
b9c7762 and 1929ffd moved or deleted. All are inert at runtime, but they are the
rationale comments that tell the next maintainer why an assertion exists, and
they now name a file that no longer explains it.

Implementation notes: re-anchored by what the citation is for, not uniformly.
- Four sites quoted facts ADR-0013 owns — every rule is `level: error` with no
  ignorable tier (ADR-0013:59-70), and KyberforgeCopilot's `.agent.md`-only
  scope (ADR-0013:43-46). These now cite ADR-0013. ADRs are append-only here;
  the spec docs are refactored, which is what caused this rot.
- Two sites quoted the glob location-independence property, which no ADR owns.
  The quote was already inline and carried the full rationale, so the citation
  added a rot surface and no information — dropped, statement kept.
- sync-marketplace-mirror.sh's header attributed the mirror-not-a-profile fact
  to CONTEXT.md; the parenthetical beside it already carries the evidence, so
  the attribution is dropped rather than re-pointed.
- .pre-commit-config.yaml cited an AGENTS.md instruction that no longer exists;
  generalised to "the documented instruction".
- LESSONS.md:29 misquoted AGENTS.md's current session-start line.

Also corrects a pre-existing misattribution at tests/test-vale-wrap.sh:454:
AGENTS.md has never named bash 3.2 as a repo target (`git log -S'3.2'` on it is
empty). LESSONS.md and the script headers do.

Impact: no behaviour change. test-check-vale-style-sync.sh and test-vale-wrap.sh
both pass (42 passed, 0 failed).

tests/test-vale-wrap.sh

@@ -451,8 +451,9 @@ fi
 # cover anything new: it omitted scripts/lib/batch-run.sh — the shared runner
 # this branch introduced, whose own header (batch-run.sh:9-11) documents it as
 # bash-3.2-safe — along with four other scripts/*.sh. Deriving the list means a
-# new script is covered the moment it lands. AGENTS.md names bash 3.2 as an
-# explicit repo target, so the scope is four globs, each floor-asserted below:
+# new script is covered the moment it lands. LESSONS.md and the script headers
+# name bash 3.2 as an explicit repo target, so the scope is four globs, each
+# floor-asserted below:
 #   - scripts/**/*.sh          — repo tooling and pre-commit hook scripts
 #   - tests/*.sh               — the runners and every regression test
 #   - plugins/*/.apm/**/*.sh   — the scripts plugins ship to users