Add codegraph_explore tool and expand exclude patterns

- Add codegraph_explore MCP tool for deep exploration with condensed output
- Expand default exclude patterns for framework build outputs (.next, .nuxt, .expo, etc.)
- Increase node ID hash length from 16 to 32 chars to prevent collisions
- Add feature request detection with UX clarification reminders
- Update README with MCP tools reference and best practices
- Update CLAUDE.md with context usage guidelines

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

src/extraction/tree-sitter.ts

@@ -19,6 +19,9 @@ import { getParser, detectLanguage, isLanguageSupported } from './grammars';
 
 /**
  * Generate a unique node ID
+ *
+ * Uses a 32-character (128-bit) hash to avoid collisions when indexing
+ * large codebases with many files containing similar symbols.
  */
 export function generateNodeId(
   filePath: string,
@@ -30,7 +33,7 @@ export function generateNodeId(
     .createHash('sha256')
     .update(`${filePath}:${kind}:${name}:${line}`)
     .digest('hex')
-    .substring(0, 16);
+    .substring(0, 32);
   return `${kind}:${hash}`;
 }