fix(automation): keep completed once tasks completed on schedule re-anchor (#504)

[TYRMars]

Summary

Fixes #504.

recomputeNextRun (packages/automation/src/task.ts) hard-coded previousRun = undefined when re-seeding next_run_at after a schedule edit. For an interval schedule that's harmless, but for a once schedule last_run_at is the only "already fired" signal — so passing undefined resurrected a finished one-shot: it wrote the original, now-past run_at back into next_run_at, making the task immediately due again on the next tick.

The single caller (automation-routes.ts PATCH handler) fires on any request carrying a schedule key — including a UI that re-sends the unchanged object on save — so editing an unrelated field (rename, model change) would silently re-execute the one-shot prompt's real side effects (backup / report / deploy).

Fix

Anchor on the task's own last_run_at instead of undefined:

setNextRunAt(task, scheduleNextAfter(task.schedule, task.last_run_at, now));

• Never-run task: last_run_at === undefined, so interval re-anchoring is byte-for-byte unchanged.
• Completed once: last_run_at is present → scheduleNextAfter returns undefined → the task stays completed.
• Interval that has run: anchors at last_run_at + interval; the existing skip-forward loop still guarantees a result strictly after now.

Tests

• New regression test: a completed once stays next_run_at === undefined / not-due after recomputeNextRun.
• Existing "reseeds an interval schedule for a never-run task" test still passes unchanged.

node --test packages/automation/src/task.test.ts → all 22 tests pass. (The unrelated store.test.ts failure is pre-existing in this environment — @jarvis/store is not installed — and reproduces on the untouched tree.)

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https://claude.ai/code/session_01ShHwvKnfC9aaPhXxn5kpMp

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