feat(rag): index markdown KB — chunker, embed client, delta importer, Sources page

Phase 02 (story: import documents):

- fence-aware markdown chunker (heading sections, 200-char overlap,
  heading anchor on every chunk, 1200-char hard cap, fence blocks
  kept atomic and split under the cap)
- LLMClient over aipi (LiteLLM) reusing the openai client's httpx
  transport to send a clean {model, input} payload — the openai SDK
  injects encoding_format, which aipi's openai_like group rejects;
  token-budget batching + halving retry for the endpoint's
  ~1024-token per-request input cap
- two-phase per-file upsert importer: sha256 delta (unchanged skip),
  atomic commit, A9 exclusion walk, per-source prune, per-file error
  tolerance (rollback + log + continue, non-zero CLI exit), adaptive
  re-chunk at half target for URL-dense files the endpoint rejects
- scripts/import_docs CLI (repeatable --source, --prune, --limit,
  defaults ~/Homelab + ~/Deployments)
- GET /api/docs with per-doc chunk counts; Sources page wired to the
  real endpoint (stat cards, full-width a11y table, designed empty
  state, DOM-built rows — no innerHTML)
- tests: 63 passed (chunker/llm/importer units, docs API + importer
  integration), story E2E 3/3 (real endpoints, in-thread import);
  app/ coverage 98%
- real KB imported: 672 docs / 8969 chunks in ~3m, idempotent
  re-run (672 unchanged, 0 batches)
- harness: .agent/validate.sh now gates through uv (pytest +
  coverage >90% + ruff + pyright) instead of system python3

app/main.py

@@ -14,6 +14,7 @@ from fastapi import FastAPI
 from fastapi.staticfiles import StaticFiles
 
 from app.api.chat import router as chat_router
+from app.api.docs import router as docs_router
 from app.api.health import router as health_router
 from app.api.suggestions import router as suggestions_router
 from app.config import get_settings
@@ -33,6 +34,7 @@ def create_app() -> FastAPI:
     # API routes first so they take precedence over the catch-all static mount.
     app.include_router(health_router, prefix="/api")
     app.include_router(suggestions_router, prefix="/api")
+    app.include_router(docs_router, prefix="/api")
     app.include_router(chat_router, prefix="/api")
 
     static_dir = Path(settings.static_dir).resolve()