Add project_archives table and MCP tools (CF-264)

- Created migration 009: project_archives table with semantic search
- Implemented archives.ts: archiveAdd, archiveSearch, archiveList, archiveGet
- Registered archive tools in index.ts and tools/index.ts
- Archive types: session, research, audit, investigation, completed, migration
- Uses project_key (TEXT) FK to projects table
- Tested: archive_add and archive_list working correctly

Replaces filesystem archives with database-backed storage.
Eliminates context pollution from Glob/Grep operations.

Task: CF-264
Session: session_20260119111342_66de546b

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/index.ts

@@ -63,6 +63,7 @@ import {
   sessionProductivityAnalytics,
   sessionPatternDetection,
 } from './tools/session-docs.js';
+import { archiveAdd, archiveSearch, archiveList, archiveGet } from './tools/archives.js';
 
 // Create MCP server
 const server = new Server(
@@ -597,6 +598,41 @@ server.setRequestHandler(CallToolRequestSchema, async (request) => {
         );
         break;
 
+      // Archives
+      case 'archive_add':
+        result = await archiveAdd({
+          project: a.project,
+          archive_type: a.archive_type,
+          title: a.title,
+          content: a.content,
+          original_path: a.original_path,
+          file_size: a.file_size,
+          archived_by_session: a.archived_by_session,
+          metadata: a.metadata,
+        });
+        break;
+      case 'archive_search':
+        result = await archiveSearch({
+          query: a.query,
+          project: a.project,
+          archive_type: a.archive_type,
+          limit: a.limit,
+        });
+        break;
+      case 'archive_list':
+        result = await archiveList({
+          project: a.project,
+          archive_type: a.archive_type,
+          since: a.since,
+          limit: a.limit,
+        });
+        break;
+      case 'archive_get':
+        result = await archiveGet({
+          id: a.id,
+        });
+        break;
+
       default:
         throw new Error(`Unknown tool: ${name}`);
     }