Add TanStack Intent maintainer skills for the Supabase collection adapter

[ivasilov]

What to build

Adopt TanStack Intent's maintainer workflow for @supabase-labs/tanstack-db, following the TanStack Intent maintainer quick start:

https://tanstack.com/intent/latest/docs/getting-started/quick-start-maintainers

This issue is about creating and shipping agent-consumable skills for this library, not adding a runtime Intent API to the Supabase collection adapter. The goal is to make it easier for AI agents and coding assistants to use this package correctly by giving them versioned, package-local guidance about the adapter's APIs, patterns, limitations, and common failure modes.

The implementation should run the TanStack Intent scaffolding flow, use the generated prompt to discover the package's domain and usage patterns, and commit the resulting skills/ tree plus the _artifacts/ files that explain how the skills were produced. The first skill set should cover the package's core tasks: creating Supabase-backed TanStack DB collections, configuring keys and schemas, using Realtime safely, understanding query pushdown and client-side fallback behavior, and avoiding common mistakes with large result sets, RLS, and mutation semantics.

The package should also be configured for publishing Intent skills. That includes updating package.json as required by npx @tanstack/intent@latest edit-package-json, adding the validation/staleness workflow from npx @tanstack/intent@latest setup, and documenting how maintainers should validate and refresh skills as the package evolves.

Acceptance criteria

• Run or follow the TanStack Intent maintainer scaffold flow for this package.
• Add an initial skills/ tree for @supabase-labs/tanstack-db with package-specific guidance.
• Commit the generated _artifacts/ files needed to audit and refresh the skill set.
• Configure package.json so the skills ship with the npm package.
• Add the TanStack Intent skill validation/staleness workflow.
• Verify the skills with npx @tanstack/intent@latest validate.
• Document the maintainer workflow for updating stale skills after package changes or releases.

Blocked by

None - can start immediately.