📝 docs: sync README / HANDOFF / CLAUDE / skill / design for fb-31

- README 명령 표 에 `kebab ingest-file` + `kebab ingest-stdin` 두 row + MCP tool list 4 → 6.
- HANDOFF post-도그푸딩 항목 한 줄.
- CLAUDE.md `_external/` 디렉토리 + naming convention 한 줄.
- integrations skill — Recipe D (agent fetched web doc) + MCP tool list 갱신.
- design §6.7 `_external/` subdirectory 절 신설.

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

integrations/claude-code/kebab/SKILL.md

@@ -86,10 +86,25 @@ Since v0.4.0, `kebab` exposes an MCP (Model Context Protocol) stdio server. Conf
 }
 ```
 
-Claude Code spawns `kebab mcp` at session start; the process stays alive across all tool calls so SQLite / Lance / fastembed are hot after the first call. 4 tools available: `search` / `ask` / `schema` / `doctor`. Same wire shapes as the CLI `--json` mode — see `Two surfaces, pick the right one` above for the same guidance.
+Claude Code spawns `kebab mcp` at session start; the process stays alive across all tool calls so SQLite / Lance / fastembed are hot after the first call. 6 tools available: `search` / `ask` / `schema` / `doctor` / `ingest_file` / `ingest_stdin`. Same wire shapes as the CLI `--json` mode — see `Two surfaces, pick the right one` above for the same guidance.
 
 If your host doesn't support MCP, the CLI subprocess pattern (`kebab search --json` / `kebab ask --json`) above continues to work.
 
+## Recipe D — agent fetched a web doc, save to KB
+
+When you've fetched a markdown article (e.g. via WebFetch) that the user might query later:
+
+1. Call MCP tool `ingest_stdin` with:
+   - `content`: the markdown body
+   - `title`: a stable title (article H1 or page title)
+   - `source_uri`: the URL you fetched from
+
+The doc lands in `<workspace.root>/_external/<hash>.md` and is indexed for `search` / `ask` immediately. Subsequent calls with identical content are no-ops (incremental ingest detects unchanged hash).
+
+Don't loop ingest the same article — content-hash dedup makes it safe but wastes embedding cost.
+
+For files already on disk that the user references, prefer `ingest_file` with the path — kebab handles the copy + dedup.
+
 ## Workflow recipes
 
 **Recipe A — user asks an internal-context question, you want grounded answer:**