feat(rules_dart,rules_flutter): enhance Bazel rules with workers and linting fixes

[yesudeep]

Summary

This PR introduces rules_flutter, a comprehensive Bazel ruleset for Flutter applications, and enhances rules_dart with advanced features. Both rulesets are designed for BCR (Bazel Central Registry) publication with hermetic, cross-platform support.

Key Features

rules_flutter (New)

Category	Features
Core Rules	flutter_library, flutter_binary, flutter_test, flutter_app
Build Targets	Web, Android, iOS, macOS, Linux, Windows
SDK Management	Hermetic SDK download with version pinning
Toolchain	Formal toolchain model following Bazel best practices
Persistent Workers	Analyzer and hot-reload workers for incremental builds
Coverage	LCOV instrumentation with collect_coverage=True
OCI Support	Docker/container rules (temporarily disabled pending aspect_bazel_lib fix)
Gazelle Extension	Go-based extension for BUILD file generation from pubspec.yaml
IDE Aspects	IntelliJ, VSCode, Cursor, Zed, and Antigravity project generation
DevTools	flutter_devtools rule for debugging and profiling
Golden Tests	flutter_golden_test for visual regression testing
Analytics	disable_analytics=True for hermetic CI builds

rules_dart Enhancements

Category	Changes
Persistent Workers	Added worker infrastructure with flagfile support
Incremental Compilation	BFS-based module dependency tracking
Build Event Protocol	Integration for build metrics
Starlark Dependency Resolution	Pure Starlark pubspec.lock parser (no shell scripts)
RBE Testing	CI workflow for Remote Build Execution compatibility
IDE Aspects	Cursor, Zed, and Antigravity integration
Runfiles Fix	Include pubspec.yaml in dart_library runfiles for test support
Documentation	ELI5 explanations and ASCII data flow diagrams
Linting Fixes	Fixed Starlark lint issues across all modules

New Features (This Update)

Starlark-native Dependency Resolution (private/pubspec_parser.bzl)

• Pure Starlark YAML parser for pubspec.lock
• pub_package repository rule for downloading from pub.dev
• dart_deps module extension for Bzlmod integration
• Eliminates need for shell-based pub get

RBE Testing Workflow (.github/workflows/rules_dart_rbe.yml)

• Remote caching compatibility tests
• Sandbox hermeticity validation
• Action determinism verification
• Build metrics and profiling with BEP output

IDE Integration Aspects

IDE	Dart Support	Flutter Support	Generated Files
Cursor	aspects/cursor.bzl	aspects/cursor.bzl	settings.json, AI rules, context.md
Zed	aspects/zed.bzl	aspects/zed.bzl	settings.json, tasks.json, keymap.json
Antigravity	aspects/antigravity.bzl	aspects/antigravity.bzl	GEMINI.md, context.json

Flutter DevTools (devtools.bzl)

• Launch DevTools with configurable features
• Inspector, Performance, Memory, Network, Logging, CPU Profiler
• Automatic VM service connection

Golden Test Support (golden.bzl)

• flutter_golden_test for screenshot comparison
• flutter_update_goldens for updating references
• flutter_golden_report for HTML diff reports
• Configurable pixel difference threshold

CI Fixes

Fix	Description
go.sum	Added go.sum for Gazelle extension in rules_flutter
sdk_root	Changed from filegroup to single file (version) for toolchain
grpc_app example	Fixed lints package version, imports, and analysis_options

Files Changed

• 130+ files changed
• ~18,000 lines added
• New Flutter ruleset with complete CI workflow
• Enhanced Dart ruleset with worker support and Starlark dependency resolution
• gRPC Flutter example with Envoy proxy configuration
• RBE testing workflow
• IDE integration for Cursor, Zed, and Antigravity

Testing

• Smoke tests: Windows, macOS, Linux
• Bazel builds: All platforms
• gRPC example: Flutter analyze + build
• Starlark lint: buildifier passes
• All CI checks passing