[test] Add shell test fixture infra for diagnosis detection logic (verify follow-up from #53)

[kiki830621]

Problem

From verification of #53 (PR #58):
「跑 find tests/ 與 *.bats 在整個 repo:zero 結果。Plugin 沒 test infra。Implementation Complete 的「Smoke Tests (manual — 4/4 PASS)」是 self-reported 的人工跑 jq,沒記錄 input fixture、沒記錄 reproduce 命令、沒 commit 到 repo」
— Source: team:devils-advocate (HIGH structural)

Repo 的 markdown skill 沒有自動化 test infra。所有 jq filter / regex / shell logic 都靠 manual smoke test → self-reported PASS → commit。半年後 jq 升版改變 (?m) 行為、或 contributor 把 regex 改錯,沒有自動化 catch。

Type

test (infrastructure)

Priority

P3 (structural debt — risk grows over time)

Strategy

1. 在 plugins/issue-driven-dev/tests/ 加 shell test fixture infra(bats 或純 bash)
2. 為現有 jq detection logic 寫 fixture:
   • tests/fixtures/comments/canonical.json — 真 diagnosis comment
   • tests/fixtures/comments/quoted.json — quoted history (> ## Diagnosis)
   • tests/fixtures/comments/mid_text.json — inline mention
   • tests/fixtures/comments/leading_ws.json — ## Diagnosis (related idd-all: 增加 HITL（attended）模式 — direct-commit + 允許 sub-skill AskUserQuestion #1 leading-ws follow-up)
   • tests/fixtures/comments/fenced.json — code block ## Diagnosis (related idd-all: direct-commit mode 加 passive warning (dirty tree / on default branch) #2 fenced follow-up)
3. Test runner: tests/diagnosis-detection.sh 跑 jq filter 對每個 fixture,assert expected output
4. CI integration (若有 CI infra)

Acceptance

• Test fixture directory created with hand-crafted comment bodies
• Shell test runner exists and runs bash tests/diagnosis-detection.sh
• All 5 cases (canonical / quoted / mid-text / leading-ws / fenced) → expected output
• Doc: explain how to add new fixture for future regex changes

Related

• fix: idd-all-chain Step 0.4 jq filter use anchored regex (avoid false-positive on quoted text) #53 (parent — fix that motivated test infra need)
• cluster: chain follow-ups (#49 docs cross-link + #53 jq regex anchor) #58 (PR with self-reported smoke tests)

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