v0.39.0 — decision-grounding

Topic-anchored decisions with read-time grounding, doc≠graph drift detection, a gated capture flow, and heal.

New

• topic anchor on decisions + the query contract (current/history/rejected/collisions) — the join key for drift detection. Defaulted, so existing graphs need no migration.
• Read-time grounding — the PreToolUse hook now surfaces a file's topic-anchored decisions with doc-precedence framing ("follow the graph, not a stale doc") + what they rejected.
• doc≠graph drift — a deterministic anchor-stale check (a file orphaned to a superseded decision) in hunch drift (CI-gateable) and doctor.
• Capture — hunch_capture_decision (grilling protocol + capture-session token) and hunch_current_decision. The existing hunch_record_decision is now gated: a store-scoped uniqueness guard refuses a second live decision per topic (a cross-store supersede that can't close its target is refused, never silently leaving two live), with an optional capture token.
• hunch reconcile-topics — surfaces >1-live-per-topic collisions a git merge can introduce.
• hunch heal + /capture /heal slash commands (scaffolded by hunch init).

Compatibility: fully additive and backward-compatible — topic defaults to null, no schema-version bump, existing decisions load unchanged.