refactor(agents): migrate .agent/ planning tree to .agents/

Standardize on the .agents/ directory (shared with project skills):
phases/, user_stories/, reports/, screenshots/, validate.sh, and
phase-sessions/ + pipeline.log all move to .agents/ (git mv preserves
history; runtime artifacts move alongside).

Updates every reference in AGENTS.md, README.md, .gitignore, app
docstrings, and test story headers. Historical KB content in data/
and the runtime pipeline.log transcript are left untouched.

.agents/reports/09_story_retrieval_quality.a1.md

@@ -0,0 +1,15 @@
+Phase 09 is complete. Final report:
+
+**Phase 09 report — commit `7e8d147`** (36 files, +2021/−293)
+
+- **A7 hybrid retrieval:** cosine top-100 ∪ Postgres FTS top-30 (stored `tsvector` + GIN, OR-tsquery), RRF k=60, LOCKED tiebreak. Fusion iteration = vector window 30→100: measured `gitlab.md:1` double-hit 0.02212 > template 0.01639 → **"How did I install gitlab?" now ranks gitlab.md #1** ✓
+- **A8 gate:** LOW only when best cosine < 0.62 **and** `fts_hits == 0`; `fts_hits` in per-turn log + `query_log` (migration 0002, nullable)
+- **A9 scope:** `md,markdown,txt,yaml,yml,json,py` (stdlib-only chunkers: YAML `---`/top-level keys, JSON top-level keys, `ast` defs/classes), dot-prefixed paths skipped, `--prune` drops filter-outs, per-format summary counts
+- **Live KB re-import:** 520 docs / 2774 chunks / 0 errors in 72s; **zero dot-prefixed paths**; k8s/backup/dns questions all ground correctly
+- **Gates:** 174 unit+integration passed · coverage 98% (>90%) · ruff + pyright clean · all 9 E2E suites green in isolation, incl. new `test_retrieval_quality.py` (4 tests: multi-format import, gitlab grounding, FTS-beats-vector, sourdough deflection)
+
+**Deviations (flagged per protocol, not silent):**
+- "sourdough → LOW" is **unmet at the locked 0.62**: measured off-topic best-cosine floor with the real `embed` model is **0.73** (battery: off 0.61–0.73, on 0.65–0.84 — the phase's 0.41–0.58 assumption was too low), so the gate answers. Fix when you want it: `BOR_RELEVANCE_THRESHOLD≈0.77` (then salsa/travel/sourdough deflect; common-word off-topic like tire/pizza still answers via the owner-approved FTS-OR).
+- `gitlab-compose.yaml` lands **#3, not top-2** (sits at vector rank 483; no sane window lets it outrank the template's double-free 1/61 term).
+
+Next pending: `10_story_document_viewer.md`.