fix(631): quote a record title whose unquoted # was a YAML comment

Third latent defect surfaced purely by running scripts/tests in CI — and this one was
already red on origin/main, where test_frontmatter_reader_matches_pyyaml_on_every_real_record
fails.

`api/paging-zero-based.md` carried an UNQUOTED plain scalar title ending
"... (#616, #633)". In YAML a space followed by `#` starts a COMMENT, so PyYAML reads the
title as truncated at "(#616," while the hand-written dependency-free reader keeps the
whole line. PyYAML is correct per spec; the record's title was genuinely losing "#633)"
for any spec-compliant consumer, which includes MemPalace's ingest.

Fixed by quoting the scalar; both parsers now agree byte-for-byte.

Asked "instance or class?" before fixing: swept every frontmatter field of all 179
records under both parsers and compared. This is the ONLY divergence in the corpus, so a
one-line fix is the right scope — no lint rule needed, and #621's structural guard
already makes a parse FAILURE loud (this was a parse-to-different, which no structural
check can see).

216 passed under jq 1.8.2 and jq 1.6.

Refs #631

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/decisions/records/api/paging-zero-based.md

@@ -1,6 +1,6 @@
 ---
 key: api.paging-zero-based
-title: 2026-07-25 — Paging is 0-based everywhere; every wrapper must say so (#616, #633)
+title: '2026-07-25 — Paging is 0-based everywhere; every wrapper must say so (#616, #633)'
 status: active
 since: '2026-07-25'
 supersedes: none