fix(bootstrap): reconcile collections on cached startup

[bobbwal]

Description

Reconciles code-defined collection document types when bootstrap is satisfied from the KV cache.

Fixes #1014

Changes

• Register code-defined collection document types after hydrating the cached bootstrap state.
• Restore document-backed operations, including slug availability checks, for collections added without a SonicJS version bump.

Testing

Unit Tests

• Existing document-type registration tests pass.
• npm test --workspace=packages/core -- document-types-seed.test.ts

E2E Tests

• Not added; this is a bootstrap-path fix with no UI changes.

Screenshots/Videos

N/A

Checklist

• Code follows project conventions
• Tests passing
• Type checking passes
• No console errors or warnings
• Documentation updated (not needed)

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