[Fix] Prevent stale PR review actions

[daniel-lxs]

Fixes three defects in the PR review offer plumbing on develop:

1. Offer resurrection race — attachPendingPrReviewActionMessage used GET-then-SET, so an offer claimed by a typed reply in between was silently recreated with live buttons that dispatch the superseded follow-up. The message id is now attached in a single atomic Lua script (KEEPTTL) that no-ops when the record is gone.
2. Index orphaning race — claimPendingPrReviewActionsForThread read and deleted the conversation index in separate operations, so offers indexed concurrently were dropped unclaimed and could never be retired by a later reply. The read, clear, and claim now run in one atomic script.
3. Resume host inheritance — snapshot-resume source-control stamps could inherit the source run's host under an explicitly different provider, resolving repositories against the wrong instance. The host is now only inherited together with the provider.

Includes mocked-Redis tests for both scripts and a DB-backed test for the host inheritance guard.

🤖 Generated with Claude Code

[roomote-roomote]

No code issues found. See task

• packages/sdk/src/server/lib/task-runs/pr-review-action.ts:166 The 50-iteration cap left additional pending offers indexed and live after a typed reply. The new atomic Lua claim drains the entire conversation index, so no capped remainder remains.

_{Reviewed 3cbab5b}