feat: add @opencode-ai/models sdk

[vimtor]

Summary

Adds the official Models.dev TypeScript SDK as @opencode-ai/models.

SDK

• zero-dependency Promise client for /api.json, /models.json, and /catalog.json
• optional Effect client at @opencode-ai/models/effect
• bundled offline catalog at @opencode-ai/models/snapshot
• hand-written public types checked for exact compatibility with core Zod schemas
• generated model-family types
• browser-safe requests with custom fetch, headers, abort signals, and structured errors

Packaging

• renames the internal workspace package to @models.dev/core
• publishes compiled ESM and declarations from dist
• builds automatically during npm pack and includes the MIT license
• keeps the root client independent of Effect, Zod, core, and snapshot data

Releases

• adds manual semver and daily data-release workflows
• derives versions from npm rather than storing release versions in git
• skips scheduled releases when snapshot data is unchanged
• publishes with npm trusted publishing and provenance
• propagates registry failures and restores locally modified release files safely

Verification

• bun validate
• cd packages/sdk && bun run test (23 tests)
• cd packages/sdk && npm pack --dry-run --json
• Node import smoke tests for root, snapshot, and Effect entrypoints
• cd packages/web && bun run build

Release Setup

@opencode-ai/models@0.0.1 is currently a placeholder, so the first SDK release will be 0.0.2. Before publishing, configure npm trusted publishing for anomalyco/models.dev and .github/workflows/publish-sdk.yml.