feat(example): add flutter-mcp-toolkit skills and cross-platform example app

[drown0315]

What Changed

• Added 8 flutter-mcp-toolkit Claude skills under .claude/skills/ covering guide, setup, debug, inspect, control, custom-tools, CLI runtime validation, and repo-maintainer workflows
• Added a grill-me skill under example/.claude/skills/
• Added complete cross-platform Flutter example app with platform config for iOS, macOS, Android, Linux, and Windows (Podfiles, Xcode projects, Gradle config, generated plugin registrants)
• Updated example/lib/main.dart and example/CLAUDE.md with MCP toolkit integration patterns
• Added dependencies (flutter_mcp) and updated pubspec.lock
• Added .flutter_mcp/ to example/.gitignore
• Fixed review issues: removed stray nvim text from example/android/app/build.gradle, disabled GPU validation mode in the macOS debug scheme
• Applied dart format lint fixes across changed files

Risk Assessment

✅ Low: The change is well-bounded to adding MCP toolkit instrumentation and supporting platform files to the example app, all previous review findings have been addressed, and the new code follows standard documented patterns without material bugs or risks.

Testing

Verified all three fix categories from commit eeaf52e: 1) nvim text cleanup — confirmed no stray nvim in build.gradle 2) flutter_mcp .gitignore — confirmed .flutter_mcp/ entry at line 27, git check-ignore confirms cache paths are properly ignored, no tracked artifacts remain 3) GPU validation removal — confirmed enableGPUValidationMode removed from Xcode scheme Ran both test suites: root package (1 test) and example app (8 tests) — 9/9 passed. Worktree restored to clean state.

Evidence: nvim-check

$ grep -rn 'nvim' example/android/app/build.gradle
(no output — no nvim text found)

Evidence: gpu-validation-check

$ grep -n 'enableGPUValidationMode' example/macos/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
(no output — GPU validation mode removed)

Evidence: gitignore-check

$ git check-ignore example/.flutter_mcp/cache/macos_helper/macos_visual_capture_-585b0c45b152b847
example/.flutter_mcp/cache/macos_helper/macos_visual_capture_-585b0c45b152b847

$ git ls-files -- 'example/.flutter_mcp/'
(no output — no tracked files)

Evidence: tests-root

$ flutter test
00:00 +1: All tests passed!

Evidence: tests-example

$ flutter test (example/)
00:00 +8: All tests passed!

Pipeline

Updates from git push no-mistakes

⏭️ **intent** - skipped

✅ No issues found.

✅ **Rebase** - passed

✅ No issues found.

🔧 **Review** - 3 issues found → auto-fixed ✅

• 🚨 example/android/app/build.gradle:46 - Stray text 'nvim' inserted on its own line inside the defaultConfig block. This is an editor artifact—it is not valid Groovy and will cause the Android Gradle build to fail with a syntax error.
• ⚠️ example/.flutter_mcp/cache/macos_helper/macos_visual_capture_-585b0c45b152b847:1 - 149 KB binary added under .flutter_mcp/cache/. Cache/build artifacts like this binary and its companion .swift source file are not intended to be version-controlled—they are regenerated on demand. The .flutter_mcp/ directory should be added to .gitignore or the files should be excluded individually.
• ℹ️ example/macos/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme:62 - enableGPUValidationMode = "1" added to the debug Run scheme. This enables Metal GPU validation during every debug launch, which can cause degraded frame rates and false-positive validation warnings in Xcode. Usually only toggled on when actively debugging Metal issues.

🔧 Fix: Fix stray nvim text, add .gitignore for flutter_mcp, remove GPU validation
✅ Re-checked - no issues remain.

✅ **Test** - passed

✅ No issues found.

• grep -rn 'nvim' example/android/app/build.gradle — confirmed no stray nvim text
• grep -n 'enableGPUValidationMode' example/macos/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme — confirmed GPU validation mode removed
• git check-ignore example/.flutter_mcp/cache/macos_helper/... — confirmed .flutter_mcp/ paths are gitignored
• cat example/.gitignore — confirmed '.flutter_mcp/' entry at line 27
• git ls-files -- 'example/.flutter_mcp/' — confirmed no binary artifacts tracked
• flutter test (root package) — 1 test passed
• flutter test (example/) — 8/8 tests passed

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.