fix(cache): Add package.json to plugin directory for cache dependency resolution

The bundled hook scripts use `external: ['better-sqlite3']` during esbuild,
meaning the dependency must be resolved at runtime. When hooks run from the
cache directory (~/.claude/plugins/cache/thedotmack/claude-mem/X.X.X/),
they couldn't find better-sqlite3 because:

1. Cache directory had no package.json
2. smart-install.js was hardcoded to install in marketplace directory only

This fix:
- Adds plugin/package.json declaring runtime dependencies (better-sqlite3)
- Updates build-hooks.js to auto-generate plugin/package.json from main package.json
- Updates smart-install.js to detect execution context (cache vs marketplace)
  and install dependencies in the correct location

The script now detects if it's running from cache (via path pattern matching)
and installs dependencies there, where the hooks actually execute.

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

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

scripts/build-hooks.js

@@ -58,6 +58,26 @@ async function buildHooks() {
     }
     console.log('✓ Output directories ready');
 
+    // Generate plugin/package.json for cache directory dependency installation
+    // The bundled hooks use `external: ['better-sqlite3']` so dependencies must be
+    // installed at runtime. This package.json enables npm install in the cache directory.
+    console.log('\n📦 Generating plugin package.json...');
+    const pluginPackageJson = {
+      name: 'claude-mem-plugin',
+      version: version,
+      private: true,
+      description: 'Runtime dependencies for claude-mem bundled hooks',
+      type: 'module',
+      dependencies: {
+        'better-sqlite3': packageJson.dependencies['better-sqlite3']
+      },
+      engines: {
+        node: '>=18.0.0'
+      }
+    };
+    fs.writeFileSync('plugin/package.json', JSON.stringify(pluginPackageJson, null, 2) + '\n');
+    console.log('✓ plugin/package.json generated');
+
     // Build React viewer
     console.log('\n📋 Building React viewer...');
     const { spawn } = await import('child_process');