feat(skills): add Claude Code skills for consuming Remix

[tilucasoli]

What

Adds three task-shaped Claude Code skills (plus a shared reference) that help downstream developers consume Remix in their own Flutter apps.

packages/remix/skills/
├── shared/find-remix-source.md        # locate installed package + read real API
├── remix-theming/                     # app-wide RemixTheme / Fortal / tokens
├── remix-component-styling/           # per-component styler chains
└── remix-material-migration/          # Material → Remix conversion (+ MAPPING.md)

Design decisions

• Read from source, never memory. Remix styler names are non-uniform (RemixButtonStyler vs RemixCardStyle vs the three RemixSelect*Style classes) and change between versions. Every skill opens with a gate that confirms class/method/constructor names against the resolved package source. The shared reference encodes the pub-cache / package_config.json resolution and grep recipes once.
• B1 / B2 boundary. remix-theming owns tokens + scope; remix-component-styling references existing tokens and defers to theming when no scope exists.
• Tiered migration. MAPPING.md splits Material widgets into auto-convert (1:1), flag-as-TODO (near-match), and leave-untouched (layout/navigation). No silent semantic changes. Migration also translates Material styling into the equivalent Remix chain.
• Self-verification. dart analyze on touched files is a required final step in every skill (non-negotiable in migration, which rewrites already-compiling code).
• Trigger disambiguation. Descriptions draw hard lines — app-wide vs single-component vs explicit Material conversion — and cross-reference each other.

Follow-ups (deferred)

• Distribution / installing into a consumer's .claude/skills/.
• Stamping the skill bundle with the Remix release version for the runtime mismatch check.

🤖 Generated with Claude Code