Prepare mcp_dart 2.4.1 release

[leehack]

Summary

• prepare the stable mcp_dart 2.4.1 SDK release while leaving mcp_dart_cli at 0.2.0
• restore the published package's Pana score from 140/160 to 160/160 under Pana 0.23.18 and Dart 3.13.1
• update exact-version changelog, release metadata, security policy, runbook, and release-facing documentation

Root cause

The published 2.4.0 archive has three Dart 3.13 analyzer diagnostics. PR #361 fixed all three on current main, but Pana's temporary monorepo formatting still treated selected nested-package files as Dart 3.13 sources instead of using those packages' declared language versions. File-level language markers now preserve the existing package minimums without changing runtime, public API, or MCP protocol behavior.

This is a patch release because the unreleased Streamable HTTP logging work hardens diagnostics without adding or changing public API or wire behavior. An exact API comparison against published 2.4.0 reports zero breaking and zero non-breaking API changes.

Validation

• Pana 0.23.18 / Dart 3.13.1: 160/160
• clean dart pub publish --dry-run: 0 warnings
• Dart 3.13.1 format, analyze, Core tests, docs, release metadata and workflow-security suites
• Dart 3.4 minimum-SDK consumer, analysis, web compile, and serialized Core suite
• Dart 3.12 CLI analysis, compile/version smoke, tests, and TypeScript/Python E2E
• API compatibility against published 2.4.0, 2.3.0, and the allowlisted 2.2.2 baseline
• pinned Core/Tasks/schema audits and 2025/2026 official conformance
• TypeScript/Python bidirectional, legacy SSE, browser, and Flutter Web interoperability
• Anthropic, Gemini, fetch, Jaspr, and Flutter nested example gates

Release boundary

This PR is intentionally draft. Merging a release-prep PR authorizes the automatic release, so merge requires separate explicit approval.

[Copilot]

Pull request overview

Prepares the mcp_dart SDK for the 2.4.1 stable release (keeping mcp_dart_cli at 0.2.0), primarily by updating release/version documentation and adding file-level Dart language markers so tooling (notably Pana’s monorepo formatting) respects each nested package’s declared minimum language version.

Changes:

• Bumps the SDK stable version to 2.4.1 across the root pubspec, release metadata, changelog, and user-facing docs.
• Adds // @dart=... language version markers to CLI and example sources to align analysis/formatting with each package’s minimum SDK.
• Updates the release-metadata validation fixture to rewrite the SECURITY.md supported-line row via a targeted multiline regex.

Reviewed changes

Copilot reviewed 30 out of 31 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tool/release/mcp_2026_07_28_release_metadata.json	Updates sdkStableVersion to 2.4.1 for the 2026-07-28 release metadata.
test/tool/validate_release_metadata_test.dart	Adjusts SECURITY policy fixture rewriting to match/replace the full table row robustly.
ROADMAP.md	Refreshes stable-baseline references from 2.4.0 to 2.4.1.
README.md	Updates stable-version messaging, dependency snippet, and API reference link to 2.4.1.
pubspec.yaml	Bumps the root mcp_dart package version to 2.4.1.
packages/mcp_dart_cli/lib/src/utils/inspect_handlers.dart	Adds // @dart=3.12 language marker for CLI package analysis consistency.
packages/mcp_dart_cli/lib/src/update_command.dart	Adds // @dart=3.12 language marker.
packages/mcp_dart_cli/lib/src/trace_command.dart	Adds // @dart=3.12 language marker.
packages/mcp_dart_cli/lib/src/serve_command.dart	Adds // @dart=3.12 language marker.
packages/mcp_dart_cli/lib/src/inspectors/inspection_report.dart	Adds // @dart=3.12 language marker.
packages/mcp_dart_cli/lib/src/create_command.dart	Adds // @dart=3.12 language marker.
packages/mcp_dart_cli/lib/src/conformance_command.dart	Adds // @dart=3.12 language marker.
packages/mcp_dart_cli/lib/src/builders/mason_bundle_builder.dart	Adds // @dart=3.12 language marker.
packages/mcp_dart_cli/lib/src/agent_skill_command.dart	Adds // @dart=3.12 language marker.
packages/mcp_dart_cli/bin/mcp_dart.dart	Adds // @dart=3.12 language marker for the CLI entrypoint.
llms.txt	Updates the stable SDK version and associated release wording/snippet to 2.4.1.
example/jaspr-client/lib/app.dart	Adds // @dart=3.10 marker matching the example package’s minimum SDK.
example/gemini-client/test/gemini_client_test.dart	Adds // @dart=3.7 marker matching the example package’s minimum SDK.
example/gemini-client/test/fixtures/env_probe_server.dart	Adds // @dart=3.7 marker.
example/gemini-client/test/cli_smoke_test.dart	Adds // @dart=3.7 marker.
example/gemini-client/lib/gemini_client.dart	Adds // @dart=3.7 marker.
example/flutter_http_client/lib/services/streamable_mcp_service.dart	Adds // @dart=3.7 marker matching the example package’s minimum SDK.
example/flutter_http_client/lib/screens/mcp_client_screen.dart	Adds // @dart=3.7 marker.
example/anthropic-client/test/fixtures/env_probe_server.dart	Adds // @dart=3.9 marker matching the example package’s minimum SDK.
example/anthropic-client/test/anthropic_client_test.dart	Adds // @dart=3.9 marker.
example/anthropic-client/lib/anthropic_client.dart	Adds // @dart=3.9 marker.
doc/sdk-tier-1-feature-coverage.md	Updates the published stable reference to 2.4.1.
doc/quick-reference.md	Updates dependency snippet and stable-version references to 2.4.1.
doc/mcp-2026-07-28-release-runbook.md	Updates runbook steps/tag references and ^2.4.1 snippet for the follow-up release.
doc/getting-started.md	Updates install snippet to mcp_dart: ^2.4.1.
CHANGELOG.md	Finalizes the 2.4.1 section and moves the previous “Unreleased” content under it.

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