fix(lastcode): repair nightly promotion after replay

[lastobelus]

The live nightly replay exposed three blockers in the promoted checkpoint: open-PR detection queried the upstream repository, worktree cleanup lost the new upstream missing-path semantics during conflict resolution, and entrypoint fallback compared non-canonical macOS paths.

Scope GitHub PR counting explicitly to the LastCode fork, reconcile worktree removal so missing paths are safe while locked registrations still fail, and canonicalize both entrypoint paths. The existing upstream and LastCode tests cover the integrated behavior, with a focused assertion for the GitHub CLI repository argument.

Validation:

• three pending upstream nightlies replayed and published as immutable checkpoints
• PR fix(web): keep remote icon visible on hover #82 and PR fix(web): dialogs no longer block clicks after closing #86 retain identical stable patch IDs after replay
• focused checkpoint, worktree, and entrypoint tests passed
• exact-head quick CI passed all test suites; post-CI shared-config guard observed an unrelated concurrent branch setting change

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