feat(flutter-cursor-templates): introduce MCP integration and conventions in project brief

- Added optional MCP integration settings in project-brief.yaml, allowing for environment-based server configurations.
- Introduced conventions for strict package imports to enhance code organization and maintainability.
- Updated brief schema to validate new MCP properties and ensure correct usage.
- Implemented MCP JSON builder to generate .cursor/mcp.json based on project brief settings.
- Enhanced resolver to include MCP configuration in generated files when enabled.

This update improves integration capabilities and enforces coding standards across the project.

flutter-cursor-templates/templates/onboarding/ONBOARDING.md.tmpl

@@ -0,0 +1,20 @@
+# Cursor — {{PROJECT_NAME}}
+
+## Quick start
+
+1. Open this repo in **Cursor** so `.cursor/rules/` and `.cursor/skills/` load automatically.
+2. Read **`rules/universal/rule-authoring.mdc`** — how we maintain AI rules.
+3. Stack and product context live in **`project-brief.yaml`** at the repo root; regenerate `.cursor/` with `cursor_gen` after changing it.
+4. **Slash skills** (primary workflows): open the Command Palette and use the project commands, or reference:
+   - `.cursor/skills/build/SKILL.md` — end-to-end feature implementation
+   - `.cursor/skills/debug-issue/SKILL.md` — structured debugging
+   - `.cursor/skills/verify-change/SKILL.md` — pre-PR verification
+   - `.cursor/skills/explain-code/SKILL.md` — explain-only walkthroughs
+5. **Agents** (`.cursor/agents/*.mdc`) are reusable reviewer personas — attach when asking for code review or focused passes.
+6. **Custom overrides**: files under `.cursor/custom/` and `CURSOR:CUSTOM` blocks in generated files are preserved on `cursor_gen --refresh` (see generator docs).
+
+## Optional
+
+- **`integrations.mcp.enabled`** in `project-brief.yaml` — generates `.cursor/mcp.json` with env-based server entries (no secrets in git).
+- **`telemetry_opt_in: true`** — emits local telemetry helpers under `.cursor/telemetry/` (never commit usage logs if you enable logging).
+- Run **`bash tool/cursor_audit.sh`** from the project root periodically to catch stale feature rules and overly broad `alwaysApply` usage.