fix(card): seed dialog history into restored-session card

[Time4Mind]

Symptom

When a session is restored via claude --resume, its live card shows
only the new turns — the prior dialog history is never picked up.
A plain bot-restart seeds history fine.

Root cause

_ensure_seeded (handlers/notifications.py) latched
state.seed_attempted = True before reading the JSONL. A restored
session builds its card while claude --resume is still flushing the
resumed transcript, so that early read returns [] — but the flag is
already latched. By the time the full transcript lands (and the first
live event fires _ensure_seeded again), the guard short-circuits, so
nothing is ever seeded.

Traced on a live restore (f852609a "latest logs", window @6):
repost_card … events=0 right after the resume, then events=2 (only
the live turn) — never a card_seeded line. The 2.8 MB transcript on
disk has 30 end-turn boundaries that should have seeded.

Plain bot-restart works only because the JSONL is already fully written,
so the first attempt succeeds.

Fix

• Latch seed_attempted only on a successful (non-empty) seed. An
  empty read leaves it clear and retries on a later event.
• Gate the retry on the transcript mtime advancing (new
  CardState.seed_mtime) so a burst of events during the resume window
  doesn't re-parse a multi-MB JSONL each time — one stat() per call,
  full parse only when the file actually grows.
• The three non-destructive re-seed sites (stale-pause reset, carrier
  release, false-stall recovery) reset seed_mtime alongside
  seed_attempted.

Tests

tests/ccbot/handlers/test_card_seed.py:

• replaces the old test_seed_attempted_only_once (which encoded the
  buggy latch-on-empty behaviour)
• test_successful_seed_latches — non-empty seed latches
• test_empty_seed_not_latched_retries_when_transcript_lands — direct
  regression for this bug: empty → not latched → seeds once the
  transcript appears
• test_unchanged_empty_transcript_not_reparsed — mtime gate suppresses
  redundant re-parses

Full suite: 747 passed. ruff + pyright clean.

🤖 Generated with Claude Code