📝 docs: sync README / HANDOFF / CLAUDE / skill / design for fb-27

- README 명령 표 에 `kebab schema` 추가
- HANDOFF post-도그푸딩 항목 한 줄
- CLAUDE.md wire schema 절 schema.v1 / error.v1 추가
- integrations skill — schema 활용 안내 (additive)
- design §10.1 capability matrix subsection 신설

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -60,7 +60,7 @@ Read the relevant task spec's deps section before adding an import. New crates i
 
 ## Wire schema v1
 
-All `--json` output carries a `schema_version` field (`ingest_report.v1`, `search_hit.v1`, `answer.v1`, `doctor.v1`, …). Schemas live in `docs/wire-schema/v1/`. The wire shape is the contract for external integrations (Claude Code skills, MCP, etc.); breaking it requires a `*.v2` major bump and parallel-running both for one phase.
+All `--json` output carries a `schema_version` field. Current schemas: `ingest_report.v1`, `ingest_progress.v1`, `search_hit.v1`, `answer.v1`, `doctor.v1`, `reset_report.v1`, `eval_run.v1`, `eval_compare.v1`, `list_docs.v1`, `schema.v1`, `error.v1`. Schemas live in `docs/wire-schema/v1/`. The wire shape is the contract for external integrations (Claude Code skills, MCP, etc.); breaking it requires a `*.v2` major bump and parallel-running both for one phase. In `--json` mode, fatal errors emit `error.v1` to stderr as ndjson (non-`--json` mode keeps plain stderr text); exit codes 0/1/2/3 are unchanged — `error.v1.code` provides fine-grained agent branching.
 
 In-tree integration packages live under `integrations/<host>/` — currently `integrations/claude-code/kebab/` (a Claude Code skill that calls `kebab search --json` / `kebab ask --json`). Any wire schema major bump (v1→v2) MUST update each shipped integration in the same PR, same as the version-cascade rule below. Per-user trigger keywords (team / system / acronym) belong in the user's local copy of the skill, not in the repo-shipped frontmatter — keep `integrations/claude-code/kebab/SKILL.md`'s `description` generic.