fix: make FTS5 optional for template search (fixes Claude Desktop compatibility)

- Added runtime FTS5 detection in database adapters
- Removed FTS5 from required schema to prevent "no such module" errors
- FTS5 tables/triggers created conditionally only if supported
- Template search automatically falls back to LIKE when FTS5 unavailable
- Works in ALL SQLite environments (Claude Desktop, restricted envs, etc.)

This ensures search_templates() works correctly regardless of SQLite build,
while still providing optimal performance when FTS5 is available.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/database/database-adapter.ts

@@ -13,6 +13,7 @@ export interface DatabaseAdapter {
   pragma(key: string, value?: any): any;
   readonly inTransaction: boolean;
   transaction<T>(fn: () => T): T;
+  checkFTS5Support(): boolean;
 }
 
 export interface PreparedStatement {
@@ -174,6 +175,17 @@ class BetterSQLiteAdapter implements DatabaseAdapter {
   transaction<T>(fn: () => T): T {
     return this.db.transaction(fn)();
   }
+  
+  checkFTS5Support(): boolean {
+    try {
+      // Test if FTS5 is available
+      this.exec("CREATE VIRTUAL TABLE IF NOT EXISTS test_fts5 USING fts5(content);");
+      this.exec("DROP TABLE IF EXISTS test_fts5;");
+      return true;
+    } catch (error) {
+      return false;
+    }
+  }
 }
 
 /**
@@ -234,6 +246,18 @@ class SQLJSAdapter implements DatabaseAdapter {
     }
   }
   
+  checkFTS5Support(): boolean {
+    try {
+      // Test if FTS5 is available
+      this.exec("CREATE VIRTUAL TABLE IF NOT EXISTS test_fts5 USING fts5(content);");
+      this.exec("DROP TABLE IF EXISTS test_fts5;");
+      return true;
+    } catch (error) {
+      // sql.js doesn't support FTS5
+      return false;
+    }
+  }
+  
   private scheduleSave(): void {
     if (this.saveTimer) {
       clearTimeout(this.saveTimer);

src/database/schema.sql

@@ -47,7 +47,5 @@ CREATE INDEX IF NOT EXISTS idx_template_nodes ON templates(nodes_used);
 CREATE INDEX IF NOT EXISTS idx_template_updated ON templates(updated_at);
 CREATE INDEX IF NOT EXISTS idx_template_name ON templates(name);
 
--- Full-text search for templates
-CREATE VIRTUAL TABLE IF NOT EXISTS templates_fts USING fts5(
-  name, description, content=templates
-);
+-- Note: FTS5 tables are created conditionally at runtime if FTS5 is supported
+-- See template-repository.ts initializeFTS5() method