Document that DurableObjectId::name is passed through to the object

[lukevalenta]

ctx.id.name is now available inside a Durable Object addressed by name, including in the constructor and alarm handlers, since the runtime passes the name through (cloudflare/workerd#2240).

Update the ObjectId::name docs to reflect this and defer to the Durable Object ID developer docs for the full list of cases where name is None.

Add test coverage that reads state.id().name() in the Durable Object constructor to confirm the name is available before any request is handled.

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 2 untouched benchmarks

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_{Comparing lukevalenta:lvalenta/document-do-id-name (668e0e9) with main (5f2d6c9)}