Add typescript-start-workflow snippet for docs

[Duncanma]

Adds snippets/src/start-workflow.ts with a new typescript-start-workflow Snipsync marker. It connects with Connection.connect() using environment configuration and starts the example Workflow on the snippets Task Queue, the same Task Queue the existing typescript-worker-create snippet polls.

Why

The TypeScript "Set a Workflow's Task Queue" section on docs.temporal.io used a hand-written sample that called Connection.create(), a method that has never existed on Connection (temporalio/documentation#5200). Hand-written samples aren't compiled anywhere, so sourcing this one from snippets/ gets it type-checked by this repo's lint-format-build job.

Companion docs PR: temporalio/documentation#5407 (draft until this merges).

Validation

Run locally in snippets/:

• npm run build: passes
• npm run lint: passes
• npm run format:check: passes
• With Connection.connect(...) changed back to Connection.create(), tsc --noEmit fails with TS2339: Property 'create' does not exist on type 'typeof Connection'. That's the error reported in the docs issue.

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