Make worktree remove timeout configurable or resumable during cleanup

[chubes4]

Problem

bounded-cleanup-eligible-apply can fail safe removals with a fixed 5 second timeout:

reason_code: remove_failed
reason: remove failed: Process command timed out after 5 second(s).

Observed examples during a large cleanup:

• wpcom-codebox@fix-issue-117-editor-auth-redirect-loop
• wpcom-codebox@fix-issue-118-local-runtime-fixtures
• wpcom-codebox@fix-issue-120-editor-proof-workflow
• wpcom-codebox@fix-selected-page-seed-boot-timeout
• wpcom-codebox@issue-116-local-auth-preflight
• studio@fix-auto-mount-wp-config-paths
• woocommerce@fix-layered-nav-count-cache-bound

These rows had already passed cleanup eligibility checks, but removal could not complete within the fixed command timeout. Re-running sometimes helped, sometimes did not.

Desired behavior

Cleanup removal should be robust for large/slow worktrees:

• Make the remove timeout configurable for cleanup operations, or use a larger default for bulk cleanup.
• Preserve per-row revalidation before removal.
• Emit a continuation command for timeout rows.
• Distinguish timeout from unsafe state changes.

Safety expectation

A longer timeout must not weaken dirty/unpushed/primary protections. It should only give git worktree remove enough time to complete once the row has passed safety checks.