[docs] Acknowledge fenced-code false-positive in chain Phase 0.4 detection (verify follow-up from #53)

[kiki830621]

Problem

From verification of #53 (PR #58):
「test("(?m)^## Diagnosis") 仍會 match fenced code block 裡 col-0 的 ## Diagnosis。修掉 quoted / inline false-positive,但沒有完全消除「程式碼或 docs 範例」這一類」
— Source: team:devils-advocate + codex

新 regex 對 markdown fenced code block (```...```) 內 col-0 ## Diagnosis 仍誤判 match。場景:某 comment 含「the canonical pattern is ## Diagnosis」並用 code fence 展示。

Type

documentation (acknowledge limitation) OR enhancement (full markdown-aware parser)

Priority

P3 (real-world fire rate低 — canonical comment 不會在 code fence 內寫 spec example)

Decision needed

Option	Effort	Result
Doc-only fix	1 line	Add comment in SKILL.md Step 0.4: "detection 對 fenced-code 內的 heading 仍 false-positive,實際 fire 率低"
Strip fenced before scan	jq-only,~5 lines	Pre-process body: strip ```...``` blocks, then scan
Full markdown-aware	High	Use markdown parser, scan only headings outside code blocks (over-engineering)

Acceptance

• Decide which option
• If doc: add 1-line comment in SKILL.md Step 0.4
• If strip: implement + smoke test fence case → false

Related

• fix: idd-all-chain Step 0.4 jq filter use anchored regex (avoid false-positive on quoted text) #53 (parent — anchored regex fix)
• cluster: chain follow-ups (#49 docs cross-link + #53 jq regex anchor) #58 (PR that introduced fix)

Source: surfaced during /idd-verify --pr 58 (cluster #49 #53), Step 5b triage. Master report: #58 (comment)