Update workerd to 1.20260809.1 and align runtime contracts

[cnluzhang]

Summary

• Update bundled workerd to 1.20260809.1, raise the maximum tenant compatibility date to 2026-08-16, and align WDL with the new runtime behavior for module clocks, execution-context APIs, Node compatibility defaults, and SQLite R*Tree support.
• Keep Workflow identity metadata out of Node-compatible process.env by materializing it in generated host wrappers, with code-budget estimates reserving the longest legal immutable version tag.
• Preserve bounded workerd positional Error metadata in structured logs and live tail without adding serialization work when no tail subscriber is active.
• Retain @cloudflare/workers-types at 5.20260804.1 because the 0808 declarations weaken Node global types in the combined checker, and add an executable type regression gate.
• Document native Workflow deletion APIs as unsupported by WDL's custom facade and consolidate permanent rollout guidance around reader-before-writer deployment ordering.
• Harden DO restart readiness, ownership takeover, and lease-budget tests against infrastructure and wall-clock races.

Compatibility And Rollout

At compatibility date 2026-08-04 or later, both nodejs_compat and nodejs_compat_v2 are enabled by default. Workers that require the previous surface must disable both flags.

For this upgrade:

1. Complete the user-runtime and do-runtime rollout.
2. Pause Control mutations while system-runtime/Control rolls.
3. Resume mutations only after old system-runtime tasks have exited.

Validation

• npm test: 2298 passed
• npm run lint:unused
• Full integration suite: 55/55 files passed
• Durable Objects ownership integration: 11/11 passed
• Workerd configuration compilation through integration preparation
• git diff --cached --check