feat(family): the promotion engine - triggers, the three criteria, the decision log and undo (milestone 463 step 3, #4989)

The agent promotes a family idea when all three criteria hold, and no person approves it. The criteria are product text: services/family.py states them, and the promote tool's docstring names every criterion the service enforces.

- Criteria: each one vetoes on its own when its reasoning is blank. Platform terms also needs an applies-when and a platform scope; proven also needs named evidence. A veto keeps the idea a candidate and is logged, so it becomes precedent.
- Precedent: every promotion stores the decisions on the nearest ideas by meaning, plus any the caller names.
- Promotion sets canon, the applicability test and the platform scope, and opens an unassessed ledger row for each member project the promoter can write. Re-promotion moves the version past every version the idea has held.
- Retire and undo: undo reverses only the latest idea-level decision, restores its recorded before-state, and logs itself with the undone decision as its precedent. Settled here: leaving canon closes the unassessed rows but keeps the judged ones, which read as needing a recheck after a re-promotion.
- Triggers open evaluations but never promote:
  - a cross-project lineage citation ("matching #N") on a note or task write;
  - a same-meaning record in another project on a shared platform, on create, at 0.80 (measured: the known pattern's builds scored 0.79-0.82, an unrelated project's best match 0.65);
  - a milestone closing on a platform.
  Each fails open and rides the response as family_hint.
- Doors: seven MCP tools, /api/family REST endpoints, and a Family page (nav, /family) showing the criteria, the ideas, and the decision log with undo and retire.
- utils/recordHref.ts holds the one copy of "where a record opens", now shared with LessonDetailView.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/components/ProjectFamilyTab.vue

@@ -99,6 +99,7 @@ watch(() => props.projectId, load);
         What this project is built on or ships as. Ideas the family has proven
         for a platform reach every project that is one, and each project
         answers them — adopts, varies with a reason, or owes the work.
+        <router-link to="/family">The family's ideas and decisions</router-link>
       </p>
     </header>