feat: proactive thoughts — auto-ping salient ones + daily digest

She was passive (thoughts piled up 'open'; Brian had to mine the feed). Now she
brings them to him:

- Live: a thought >= PING_AUTO_SALIENCE (0.8) auto-pings — _compose_reachout writes
  a short personal text in her voice (not a thought-dump), on a cooldown
  (PING_COOLDOWN_MIN=60, AUTO only; explicit reach-outs bypass), quiet hours respected.
- Daily: maybe_daily_digest() texts a once-per-local-day summary of what she's been
  turning over (after DIGEST_HOUR=18), run from the dream cycle.
- maybe_ping gains bypass_cooldown (her deliberate reach-outs always go through).

8 new/updated tests (auto-ping above/below bar, digest once-per-day, floor/cooldown
isolation). Suite 80 green, ruff clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.env.example

@@ -45,3 +45,6 @@ FEED_REACT_PROB=0.5      # chance a new thought reacts to a feed item
 # Defaults to SUMMARY_BACKEND. Set to run her reflections/thoughts on a steerable model.
 INTROSPECTION_BACKEND=
 INTROSPECTION_MODEL=
+PING_AUTO_SALIENCE=0.8   # a thought this salient auto-pings even without an explicit reach-out
+PING_COOLDOWN_MIN=60     # min minutes between AUTO pings (explicit reach-outs bypass)
+DIGEST_HOUR=18           # local hour to send her daily "what I've been thinking" digest