Phase 45 (first slice): DocRef + doc_refs field on PlaybookEntry

Phase J keeps asking for: playbooks know which external docs they
used, get flagged when those docs drift. This commit ships the data
model; context7 bridge + drift check endpoints land in follow-ups.

Added to crates/vectord/src/playbook_memory.rs:
- pub struct DocRef { tool, version_seen, snippet_hash, source_url,
  seen_at } — one external doc reference
- PlaybookEntry.doc_refs: Vec<DocRef> — empty on legacy entries,
  serde default ensures pre-Phase-45 persisted state loads cleanly
- PlaybookEntry.doc_drift_flagged_at: Option<String> — set by the
  (future) drift-check code when context7 reports newer version
- PlaybookEntry.doc_drift_reviewed_at: Option<String> — set by
  human via /resolve endpoint after reviewing the diagnosis
- impl Default for PlaybookEntry — collapses most test-helper
  constructors from 17 explicit fields to 6-9 fields +
  ..Default::default()

Updated SeedPlaybookRequest + RevisePlaybookRequest (service.rs) to
accept optional doc_refs: the seed/revise endpoints already take the
field, downstream drift detection (Phase 45.2) consumes it.

Docs: docs/CONTROL_PLANE_PRD.md gains full Phase 45 spec with gate
criteria, non-goals, and risk notes.

Tests: 51/51 vectord lib tests green (same count as before, field
additions are backward-compat).

Memory: project_doc_drift_vision.md written so this keeps coming
back to the front of mind.

Next slices (same phase): context7 HTTP bridge in mcp-server,
/vectors/playbook_memory/doc_drift/check/{id} endpoint, overview-
model drift synthesis writing to data/_kb/doc_drift_corrections.jsonl,
boost exclusion for flagged+unreviewed entries.

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

docs/CONTROL_PLANE_PRD.md

@@ -217,6 +217,38 @@ Ship each phase before starting the next. Each ends with green tests + docs upda
 
 ---
 
+## Phase 45 — Doc-drift detection + context7 integration
+
+**Goal:** Playbooks know which external docs they were written against. When those docs change (Docker adds a feature, npm lib goes major, Terraform renames a resource), the playbook is automatically flagged. Small models never run confidently-outdated procedures — the drift signal reaches them before the next execution does.
+
+**Why this phase exists at all:** The 0→85% thesis depends on the hyperfocus lane staying valid. External doc drift invalidates the lane silently — popular playbooks can compound the wrong way, accumulating boost while growing more wrong. Phase 25 already retires playbooks on *internal* schema drift; Phase 45 is the same mechanism against *external* doc drift. This is the completion of the learning loop, not an optional add-on.
+
+**Ships:**
+- `shared::types::DocRef` — `{ tool: String, version_seen: String, snippet_hash: Option<String>, source_url: Option<String>, seen_at: DateTime<Utc> }`
+- `PlaybookEntry.doc_refs: Vec<DocRef>` — `#[serde(default)]` so pre-Phase-45 entries load as empty vec
+- `/vectors/playbook_memory/seed` + `/revise` accept `doc_refs` in the request body
+- `/vectors/playbook_memory/doc_drift/check/{id}` — manual drift check: looks up each `doc_refs[]` entry via the context7 bridge, returns per-tool `{version_seen, version_current, drifted: bool}` plus overall verdict
+- `/vectors/playbook_memory/doc_drift/scan` — batch scan across all active playbooks (scheduled path for Phase 45.2)
+- `mcp-server/context7_bridge.ts` — Bun HTTP bridge. Exposes `GET /docs/:tool/version` + `GET /docs/:tool/:version/diff?since=X` against the installed context7 MCP plugin. Gateway calls this over localhost.
+- `PlaybookMemory::compute_boost_for_filtered_with_role` — excludes entries where `doc_drift_flagged_at.is_some() && doc_drift_review.is_none()` (same rule as retired + superseded)
+- Overview model synthesis writes `data/_kb/doc_drift_corrections.jsonl` per detected drift: `{playbook_id, tool, version_seen, version_current, diff_summary, recommended_action, generated_at}`
+- Human-in-the-loop re-seal path: `/vectors/playbook_memory/doc_drift/resolve/{id}` — marks reviewed, optionally triggers `revise_entry` if procedure changed
+
+**Gate:**
+- Seal a playbook referencing Docker 24.x → doc_refs captured. Bump Docker version behind the scenes → `/doc_drift/check/{id}` returns `drifted: true, from: 24.0.7, to: 25.0.1, summary: "..."`. The boosted playbook count on next `/vectors/hybrid` query drops by 1 (drift-flagged skipped).
+- `doc_drift_corrections.jsonl` contains the overview model's synthesis for the drift with at least: summary of change, recommended action, cost/impact estimate.
+- Human calls `/doc_drift/resolve/{id}` after reviewing → playbook returns to active boost pool (or supersedes via Phase 27 if procedure materially changed).
+- Unit tests: DocRef serde default (legacy entries load as empty), drift check against mocked context7 bridge, boost exclusion when drifted+unreviewed.
+
+**Non-goals (explicit):**
+- Automatic re-seal without human review. Drift-detection → flag, not silent rewrite.
+- Cross-playbook propagation of one drift diagnosis. Each playbook reviewed individually (aggregation later if warranted).
+- Generating the updated procedure. T3 *suggests*; human or separate bot (see `bot/`) *writes*.
+
+**Risk:** Medium. The context7 bridge is new infrastructure (Bun ↔ context7 MCP plugin ↔ HTTP shape for gateway consumption). Mitigation: context7 plugin is already installed; its MCP tools return structured JSON; the bridge is thin adapter code. Start with single-tool drift check (Docker) before broadening.
+
+---
+
 ## Long-horizon domains (not in current phase sequence)
 
 The architecture was drafted with DevOps execution (Terraform, Ansible) as the eventual target. **That remains aspirational, not current scope** — we don't start wiring `terraform validate` / `ansible-lint` until the staffing domain proves the six-layer architecture at scale.