feat: add heartbeat monitor and vector memory search (Tier 2)

Heartbeat:
- HeartbeatMonitor with 5 checks: gateway, model, channels, memory, disk
- Configurable interval, failure threshold, notification channel
- Recovery notifications when health restores
- 25 new tests

Vector Memory Search:
- EmbeddingProvider interface with OpenAI, Gemini, Ollama, LlamaCpp backends
- SQLite-backed VectorStore with cosine similarity search
- Text chunker with paragraph-aware splitting and overlap
- HybridSearch merging keyword + vector results with configurable weight
- Background indexer with dirty-namespace tracking
- Graceful fallback to keyword search when embeddings unavailable
- 51 new tests

Config: automation.heartbeat + memory.embedding schema sections
Total: 950 tests passing, all types clean

src/tools/builtin/index.ts

@@ -22,6 +22,7 @@ export { createCronTools } from './cron.js';
 
 import type { Tool } from '../types.js';
 import type { MemoryStore } from '../../memory/store.js';
+import type { HybridSearch } from '../../memory/hybrid-search.js';
 import type { WebSearchConfig } from './web-search.js';
 import { shellExecTool } from './shell.js';
 import { fileReadTool } from './file-read.js';
@@ -47,11 +48,11 @@ export const allBuiltinTools: Tool[] = [
 ];
 
 /** Create memory tools that require a MemoryStore instance. */
-export function createMemoryTools(store: MemoryStore): Tool[] {
+export function createMemoryTools(store: MemoryStore, hybridSearch?: HybridSearch): Tool[] {
   return [
     createMemoryReadTool(store),
     createMemoryWriteTool(store),
-    createMemorySearchTool(store),
+    createMemorySearchTool(store, hybridSearch),
   ];
 }
 

src/tools/builtin/memory-search.ts

@@ -1,5 +1,6 @@
 import type { Tool, ToolResult } from '../types.js';
 import type { MemoryStore } from '../../memory/store.js';
+import type { HybridSearch } from '../../memory/hybrid-search.js';
 
 interface MemorySearchArgs {
   query: string;
@@ -7,13 +8,15 @@ interface MemorySearchArgs {
 
 /**
  * Creates a memory.search tool bound to the given MemoryStore instance.
- * Searches across all memory namespaces for matching content.
+ * When a HybridSearch instance is provided, uses vector + keyword search;
+ * otherwise falls back to keyword-only search.
  */
-export function createMemorySearchTool(store: MemoryStore): Tool {
+export function createMemorySearchTool(store: MemoryStore, hybridSearch?: HybridSearch): Tool {
   return {
     name: 'memory.search',
     description:
-      'Search across all memory files for a keyword or phrase. Returns matching lines with surrounding context from every namespace.',
+      'Search across all memory files for a keyword or phrase. Returns matching lines with surrounding context from every namespace.' +
+      (hybridSearch ? ' Uses semantic vector search combined with keyword matching for better results.' : ''),
     inputSchema: {
       type: 'object',
       properties: {
@@ -28,6 +31,33 @@ export function createMemorySearchTool(store: MemoryStore): Tool {
       const args = rawArgs as MemorySearchArgs;
 
       try {
+        // Try hybrid search first if available
+        if (hybridSearch) {
+          try {
+            const results = await hybridSearch.search(args.query);
+
+            if (results.length === 0) {
+              return { success: true, output: `No matches found for "${args.query}".` };
+            }
+
+            const formatted = results.map((result) => {
+              const sourceLabel = result.source === 'both' ? 'keyword+vector'
+                : result.source === 'vector' ? 'vector'
+                : 'keyword';
+              return `[${result.namespace}:${result.line}] (${sourceLabel}, score: ${result.score.toFixed(3)}) ${result.content}\n  context: ${result.context}`;
+            }).join('\n\n');
+
+            return {
+              success: true,
+              output: `Found ${results.length} match${results.length === 1 ? '' : 'es'} for "${args.query}":\n\n${formatted}`,
+            };
+          } catch (hybridError) {
+            // Fall back to keyword search on hybrid failure
+            console.error('Hybrid search failed, falling back to keyword search:', hybridError);
+          }
+        }
+
+        // Keyword-only fallback
         const results = store.search(args.query);
 
         if (results.length === 0) {