feat(wiki): add repo-scoped LLM wiki integrated with SDD workflow

[robertraf]

Summary

Adds a repo-scoped LLM Wiki (.wiki/) that accumulates high-value SDD artifacts — specs, plans, tasks summaries, review findings, and lessons learned — so future sessions consult prior work instead of rediscovering context. Introduces two new skills (/sdd:wiki-ingest, /sdd:wiki-close-loop) and a new Phase 7 "close-loop" that makes explicit what was already true: /ship is not the end of the workflow.

What changed

• skills/wiki-ingest/SKILL.md — new skill with --preliminary and --final modes; writes YAML-frontmatter markdown pages, updates index.md per type section, and appends parseable entries to log.md. All ingestion is opt-in.
• skills/wiki-ingest/scripts/wiki-init.sh — idempotent .wiki/ initializer (creates index.md, log.md, CLAUDE.md seed).
• skills/wiki-ingest/scripts/wiki-query.sh — deterministic keyword matcher over .wiki/index.md: tokenize → drop stopwords + short tokens → rank by match count.
• skills/wiki-close-loop/SKILL.md — new skill for post-merge consolidation. Uses gh to gather review comments and post-review commits, then delegates to /sdd:wiki-ingest --final with cross-links to the preliminary pages.
• skills/spec/SKILL.md, skills/plan/SKILL.md — new Step 0 consults the wiki via ${CLAUDE_PLUGIN_ROOT}/skills/wiki-ingest/scripts/wiki-query.sh before interviewing. Graceful no-op when .wiki/ is absent.
• skills/ship/SKILL.md — new Step 9 prompts to ingest spec/plan/tasks; Gotchas now flag that /ship is not terminal.
• .claude/rules/wiki-conventions.md — full schema: frontmatter fields, naming, index.md/log.md format, matching algorithm, lifecycle.
• .claude/rules/sdd-workflow.md — adds Phase 7 and broadens globs so the rule surfaces in affected skills.
• CLAUDE.md — pipeline diagram now ends in /sdd:wiki-close-loop; skills table extended.
• tests/wiki-init-tests.sh, tests/wiki-query-tests.sh — 27 shell tests (14 + 13).

Change overview

```mermaid
graph TD
SPEC[Modified: /spec] -->|Step 0: consult| Q[New: wiki-query.sh]
PLAN[Modified: /plan] -->|Step 0: consult| Q
Q --> IDX[.wiki/index.md]
SHIP[Modified: /ship] -->|Step 9: prompt| WI[New: /sdd:wiki-ingest --preliminary]
CL[New: /sdd:wiki-close-loop] --> WIF[New: /sdd:wiki-ingest --final]
WI --> INIT[New: wiki-init.sh]
WIF --> INIT
WI --> WIKI[.wiki/]
WIF --> WIKI
```

How to test

1. Validate the skill suite:
   ```bash
   bash tests/validate-skills.sh
   ```
   Expected: 15 skills tested, 210 OK, 0 FAIL.
2. Run the bundled shell tests:
   ```bash
   bash tests/wiki-init-tests.sh
   bash tests/wiki-query-tests.sh
   ```
   Expected: 14/14 and 13/13 passing.
3. Dogfood end-to-end in a scratch repo:
   • Run `/spec` for a feature — confirm Step 0 runs silently when .wiki/ is absent.
   • Run through `/plan` → `/tasks` → `/implement` → `/review` → `/ship`.
   • At `/ship` Step 9, accept the ingestion prompt — verify .wiki/spec-*.md, plan-*.md, tasks-summary-*.md are created with frontmatter.
   • Run `/spec` again for a related topic — confirm the previous page is surfaced.
   • After merging, run `/sdd:wiki-close-loop` — confirm final pages are written and related: links point to the preliminary.

Breaking changes

None. Repos without .wiki/ continue to work with /spec, /plan, /ship exactly as before. Absence of the wiki is a graceful no-op everywhere.

References

Closes #21