feat(context): add recall fusion and zvec workspace adapters

Introduce RRF-based recall fusion for personal/episodic/temporal paths,
zvec-grep workspace shadow probing for code executors, and a local
headroom proxy starter aligned with the fusion plan defaults.

Co-authored-by: Cursor <cursoragent@cursor.com>

chat-intent-router.mjs

@@ -10,6 +10,10 @@ import {
   PAGE_DATA_COLLECT_SKILL_NAME,
 } from './chat-skills.mjs';
 import { applyContextBudgetToOrchestration } from './context-budget.mjs';
+import {
+  applyRecallFusionToMemoryMerge,
+  buildRecallFusionResolvedEvent,
+} from './recall-fusion.mjs';
 import { isDirectChatSessionId } from './direct-chat-service.mjs';
 import {
   memoryLimitForIntervention,
@@ -1709,12 +1713,14 @@ export function createChatIntentRouter(options = {}) {
         agentMemoryPolicy.timeoutMs,
         'Memory V2 agent resolve',
       );
-      const memories = mergeAgentMemoryCandidates({
+      const fused = applyRecallFusionToMemoryMerge({
         personalMemories: personalResolved?.memories,
         episodicMemories: episodicResolved?.memories,
         query: text,
         limit,
+        legacyMerge: mergeAgentMemoryCandidates,
       });
+      const memories = fused.memories;
       const degraded = personalFailed
         || episodicFailed
         || Boolean(personalResolved?.degraded)
@@ -1730,6 +1736,8 @@ export function createChatIntentRouter(options = {}) {
           ? (memories.length ? 'partial_memory_resolve_failed' : 'memory_resolve_failed')
           : (memories.length ? null : (episodicResolved?.reason ?? personalResolved?.reason ?? null)),
         memories,
+        recallFusion: buildRecallFusionResolvedEvent(fused.fusion),
+        recallFusionApplied: fused.applied,
         latencyMs: Date.now() - startedAt,
       };
       agentMemoryMetrics.resolved += 1;