Add flutter-app-runtime skill for runtime inspection MCP tools

[jwren]

Add the flutter-app-runtime skill to provide runtime application discovery,
live widget inspection, layout/error diagnostics, and proactive hot reloading
via the Dart MCP server.

This skill provides the runtime management workflows referenced by the proactive
Flutter hot reload rule introduced in #228 (rules/flutter-app-runtime.md). While
the rule triggers upon .dart file modifications, this skill also equips agents
to handle non-edit observational queries about the running application without
falling back to static source code assumptions.

Key capabilities and workflows added:

• Live UI & Hierarchy Inspection: Query the live widget tree via widget_inspector
  (get_widget_tree), supporting summaryOnly: false to inspect exact immediate
  parent widgets and framework styling wrappers, and summaryOnly: true for user
  code structure.
• Layout Overflow & Error Diagnostics: Check for active RenderFlex overflows and
  framework exceptions using get_runtime_errors and inspect render box constraints.
• Proactive Hot Reload / Hot Restart: Execute hot_reload on UI modifications or
  hot_restart on foundational state/initialization changes, followed by
  verifying runtime stability.
• Application Discovery: Discover and connect to active instances via dtd
  (listDtdUris, connect, listConnectedApps) with clear fallback handling
  when no running app is connected.

Related:

• Companion rule: Add proactive Flutter hot reload rule #228
• Supersedes: Add flutter-app-runtime Agent Skill for runtime interaction and proactive hot reload #221

[gemini-code-assist]

Code Review

This pull request introduces a new skill, flutter-app-runtime, which enables interaction with running Dart and Flutter applications using Dart MCP server tools. The changes include adding the skill to the README, defining its configuration in flutter_skills.yaml, and creating a comprehensive guide in SKILL.md. The feedback recommends adding a trailing newline to the end of flutter_skills.yaml to ensure POSIX compatibility.

[gemini-code-assist]

The file does not end with a trailing newline. It is a standard practice to end all text files with a newline character to ensure compatibility with POSIX tools and avoid diff warnings.

    - https://docs.flutter.dev/tools/hot-reload