feat(world): add durable run-tree purge capability

[0xKoller]

Summary

• add an explicit run-tree purge capability to the World contract
• implement durable write fencing, idempotent retry, descendant discovery, and entity removal in world-local
• implement transactional tombstones, lineage fences, triggers, and entity removal in world-postgres
• leave world-vercel unsupported and document the separately owned workflow-server operation required before it can advertise the capability

Closes #3114 only when the managed Vercel backend is implemented; this PR alone does not provide Vercel production deletion.

Verification

• all 483 world-local tests pass, including active, absent, concurrent, restart/partial-retry, descendant, and post-delete rejection cases
• world, world-local, and world-postgres build
• world-local and world-postgres typecheck
• Biome and git diff checks pass

Constraints

Docker is unavailable in the authoring environment, so the Postgres migration/concurrency path still needs its Testcontainers CI run. The private vercel/workflow-server source is not in this repository; it must implement atomic root-tree deletion, fencing, snapshots, and owned blob-reference cleanup before world-vercel can safely expose this capability.

[changeset-bot]

🦋 Changeset detected

Latest commit: 864dc85

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 20 packages

Name	Type
@workflow/world	Minor
@workflow/world-local	Minor
@workflow/world-postgres	Minor
@workflow/cli	Patch
@workflow/core	Patch
@workflow/vitest	Patch
@workflow/web-shared	Patch
@workflow/web	Patch
@workflow/world-testing	Patch
@workflow/world-vercel	Patch
@workflow/builders	Patch
workflow	Patch
@workflow/next	Patch
@workflow/nitro	Patch
@workflow/astro	Patch
@workflow/nest	Patch
@workflow/nuxt	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
@workflow/vite	Patch

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