feat: brain-engine + brain-ui + docs — template full stack standalone

- brain-engine: server, embed, search, RAG, MCP, start.sh (standalone)
- brain-ui: source React complète, build.sh, DocsView avec tier colors
- docs: 14 pages guides humains (getting-started, architecture, sessions, workflows, agents, vues tier)
- brain-compose.yml v0.9.0: tier featured ajouté, sessions/agents par tier, coach_level, API key schema
- DISTRIBUTION_CHECKLIST v1.2: brain-engine + brain-ui + docs dans la checklist

brain-engine/queries/stale-claims.sql

@@ -0,0 +1,12 @@
+-- stale-claims.sql — Claims ouverts depuis plus de 4h
+-- Usage : sqlite3 brain.db < brain-engine/queries/stale-claims.sql
+
+SELECT
+    sess_id,
+    scope,
+    opened_at,
+    ROUND((julianday('now') - julianday(opened_at)) * 24, 1) AS age_hours
+FROM claims
+WHERE status = 'open'
+  AND julianday('now') > julianday(opened_at, '+4 hours')
+ORDER BY age_hours DESC;