feat: Enable strict lint enforcement on pre-commit

Strict enforcement now active:
- Format all changed files (auto-fix)
- Lint entire packages that have changed files
- Type-check affected packages
- Block commit if ANY warnings or errors

Impact: If you touch a file in a package with existing violations,
you must clean up the entire package before committing.

This forces incremental cleanup while preventing new violations.

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

.lintstagedrc.mjs

@@ -1,12 +1,42 @@
 // Monorepo-aware lint-staged configuration
-// NOTE: Strict enforcement is disabled until existing violations are fixed.
-// See docs/quality-rails-status.md for current status.
+// STRICT ENFORCEMENT ENABLED: Blocks commits if affected packages have violations
+//
+// IMPORTANT: This lints ENTIRE packages, not just changed files.
+// If you touch ANY file in a package with violations, you must fix the whole package.
+// This forces incremental cleanup - work in a package = clean up that package.
+//
 export default {
-  // TypeScript files - format only for now
+  // TypeScript files - lint and typecheck affected packages
   '**/*.{ts,tsx}': (filenames) => {
-    return [
-      `prettier --write ${filenames.join(' ')}`,
-    ];
+    const commands = [];
+
+    // 1. Format first (auto-fixes what it can)
+    commands.push(`prettier --write ${filenames.join(' ')}`);
+
+    // 2. Extract affected packages
+    const packages = [...new Set(filenames.map(f => {
+      const match = f.match(/^(apps|packages)\/([^/]+)\//);
+      if (!match) return null;
+      // Return package name format for turbo (e.g., "@mosaic/api")
+      return `@mosaic/${match[2]}`;
+    }))].filter(Boolean);
+
+    if (packages.length === 0) {
+      return commands;
+    }
+
+    // 3. Lint entire affected packages via turbo
+    // --max-warnings=0 means ANY warning blocks the commit
+    packages.forEach(pkg => {
+      commands.push(`pnpm turbo run lint --filter=${pkg} -- --max-warnings=0`);
+    });
+
+    // 4. Type-check affected packages
+    packages.forEach(pkg => {
+      commands.push(`pnpm turbo run typecheck --filter=${pkg}`);
+    });
+
+    return commands;
   },
 
   // Format all other files