Make hosted compute provisioning non-blocking

[mrubens]

Summary

• start first-time E2B, Daytona, and Blaxel worker artifact provisioning in the background during onboarding
• allow environment setup tasks to be created before compute is ready and keep them in an explicit waiting state
• automatically dispatch waiting tasks after provisioning succeeds
• surface provisioning failures on tasks and onboarding/settings screens with a retry path
• preserve the active artifact during replacement builds and retain startup reconciliation

Why

Hosted worker artifacts are deployment-wide, but first-time provisioning previously blocked the onboarding flow. This lets administrators continue configuring source control, repositories, and environments while the selected provider is prepared, without silently switching providers.

Validation

• focused web Vitest suite (145 tests)
• cloud-agent queue tests (16 tests)
• controller and types focused tests
• package lint for web, cloud-agents, controller, and types
• package typechecks for web, cloud-agents, controller, and types
• Prettier and git diff --check

[roomote-roomote]

No new code issues found. See task

Since the last review, the only in-scope change is commit 63bcc47, which drops the export on dispatchWaitingTasksForProvisioning in apps/web/src/trpc/commands/compute/compute-provisioning.ts to satisfy Knip. Confirmed the function is only referenced within that same file (declaration plus its single internal caller) and has no external importers, so removing the export is correct and non-breaking.

Non-blocking note (unchanged from the initial review): the persisted task failure message points to "Settings → Sandboxes" while the onboarding retry buttons navigate to the compute-config step — slightly inconsistent recovery guidance.

_{Reviewed 63bcc47}