automations: a finished reminder moved later wakes again; a late save is refused

[ZeroPoint95]

Fixes moving a finished one-time reminder later with e on /automations, which could leave the row finished.

What changed

• Cause: the edit line wrote at to the minute, so an in 2m reminder came back seconds earlier and "the next minute" could be seconds away. Store.Update then saved a new moment that had passed while the card was up; the clock said it at once and the row was finished again.
• Store.Update refuses a changed one-time moment that is not after now (… has already passed, to the second within the current minute). Store.Create is unchanged: an add answered late still runs once.
• The edit line keeps a moment's seconds (at 2026-10-14T20:33:13), and writes a moment in a fall-back's repeated hour as RFC 3339 with its offset.
• An edit is refused for a past moment only when it moves the moment, so a finished reminder can be renamed or re-said.
• automation.NextAfterChange is the one next-run rule for both cards (typed edit and the conversation's change).
• A typed save of a paused automation says still paused — resume starts it again, not a next run.
• Manual: automations.md gains a section on a change refused at save time and renaming a finished reminder, plus the refusal list; three retrieval probes. DESIGN.md and a change entry updated.

How it was checked

1. gofmt -l internal/ cmd/ printed nothing; go vet on automation, tui3, session and manual was clean.
2. go test -race ./internal/automation/ → ok.
3. go test ./internal/tui3/ -run 'Automation|Typed|Edit' → ok; -run Manual → ok.
4. go test ./internal/session/ -run 'Automation|Manual' → ok.
5. go test ./internal/manual/ → ok, with the three new probes reaching automations.
6. make changelog-check → all entries well formed.
7. Each new test failed with its production hunk reverted:
   • The owner's walk (in 2m, said, e, next minute, Save 5 seconds late) left the reminder due at once.
   • The paused card promised next Mon 19 Oct at 09:00.
   • The paused receipt said saved weekly update renamed · next Mon 19 Oct at 09:00.
   • The repeated-hour line read 01:30 EST back as 01:30 EDT.
   • The same-minute refusal said 14:30 has already passed at 14:30:05.
8. Not run: make pr-ready or the full tui3/session suites. The PR's CI runs them.

Checklist

• A change entry — docs/changes/unreleased/1837-edit-finished-reminder.md.
• The manual knows about it — internal/manual/chat/automations.md, with probes in internal/manual/chat_test.go.
• No new line in .github/known-red.txt.
• Only my own paths are staged. Commits used git add -A in a clean worktree; git diff --stat origin/dev...HEAD lists only the 11 files of this change.

🤖 Generated with Claude Code