Let actor storage own both KV surfaces

[MiguelsPizza]

Why

The synchronous and asynchronous Durable Object storage views share one SQLite owner, codec, and list compiler. Splitting the sync view into a second module created an import cycle, duplicate types, and forwarding helpers with no independent responsibility.

What changed

• Colocated SyncKvStorage with DurableObjectStorage and deleted the separate sync-kv module.
• Removed the single-implementation owner interface, duplicate list options, pass-through codec helpers, and custom iterator machinery.
• Kept compiler, codec, transaction, and pinned-check details private.
• Reused native generators and centralized generic narrowing in the decoder.

Net result: 106 fewer lines and the actor-state/sync-kv import cycle is gone.

Validation

• pnpm typecheck
• pnpm test:unit — 27 files, 799 tests
• fallow audit --base origin/main — pass; zero introduced dead code, complexity, duplication, or dependency cycles
• git diff --check

Related work

• Builds on the compile-time continuation transform in do-runtime#24.
• Lets the Rook cutover remove more consumer-side machinery in rook#143.

Draft only; do not merge without Alex explicit approval.