fix(kanban): recover cards guarded by stale PR evidence

[Oceanswave]

Fix Ready cards guarded by PR evidence even though they have never run, and allow strictly later operator promoted_manual/unblocked events to recover a previously run card. Automatic status, promoted and reclaimed events retain the duplicate-PR guard. Existing explicit handoff rules still reject same-owner/unassign/default-assignee bookkeeping.

Updated against main 7239625ae1b7, using the current kanban_db_dispatch owner module and upstream CLI guard reporting. Regression fixtures now represent prior implementer runs where duplicate-work protection applies.

Validation at 84c6359b058c: canonical runner across seven Kanban files: 116 passed, 2 platform-specific tests skipped on macOS. The systemd refusal test is explicitly Linux-scoped; it requires the Linux CI lane. Ruff and diff checks passed. Hosted CI must still execute before merge readiness can be established.

Closes #80231.

[spfcraze]

This was generated by AI during triage.

Summary:
The requeue kinds that supersede the active-PR guard include events written by automatic machinery (recompute_ready's promoted, release_stale_claims's reclaimed), so an automatic event after a PR comment can disable the guard on its own.

Problems:

• check_respawn_guard treats any later event of kind status/promoted/promoted_manual/unblocked/reclaimed as a continuation request, but kanban_db.py:4217 (recompute_ready) writes promoted automatically when a task's parents complete, and release_stale_claims (~4591) writes reclaimed when a worker's claim goes stale.
• After a worker opens a PR and the card returns to ready/blocked, one such automatic event disables the guard and the dispatcher respawns the task — the duplicate-PR outcome the guard exists to prevent; the PR body's "explicit requeue" wording is narrower than the implementation.

Solution:
Restrict the supersede set to operator-only kinds (promoted_manual, unblocked), or require an operator actor field on promoted/reclaimed before they count.

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Checked against 314b6dd — the tip of fix/dispatch-respawn-guard-json-80231 when this was written — and 9d4ef04, main at the same moment.