feat: cloud-first consolidation routing + graceful backend fallback

Nail down which backend each LLM path uses, and make the dream cycle resilient to
a backend being down (the MI50 outage left profile/era/narrative — pinned to mi50
with no fallback — aborting every dream cycle).

- Consolidation (summaries + profile/era/narrative) -> cloud via SUMMARY_BACKEND=
  cloud (.env, not committed). Matches the documented lesson that the MI50 is too
  slow/hot for bulk consolidation; nothing background touches the card now.
- llm.complete_with_fallback(): try the primary backend, fall back to cloud on
  error (re-raise if already cloud / no key). Wired into reflect + think so the
  introspection voice (3090/dolphin) survives the gaming PC being powered off.
- dream coherence stage is now fault-isolated: a rebuild failure logs + continues
  instead of sinking the whole pass (reflection still runs).
- .env: removed stale INTROSPECTION_BACKEND=mi50 (live routing is the web-switchable
  introspection_mode DB setting = dolphin/3090; the var only fed a dead fallback).

Verified: forced cycle runs consolidation on cloud, introspection on the 3090,
completes with zero MI50 calls. 206 pass, ruff clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015yrEb5qpPGv2FjyxrB7LLk

tests/test_dream.py

@@ -105,3 +105,22 @@ def test_dream_cycle_stops_when_over_budget(lyra, monkeypatch):
     assert any("stopped early" in a for a in acts)   # bailed
     assert not any("reflected" in a for a in acts)   # later stage skipped
     assert pings, "expected an over-budget ntfy push"
+
+
+def test_coherence_failure_does_not_sink_the_cycle(lyra, monkeypatch):
+    memory = lyra
+    from lyra import dream, profile
+
+    for k in range(3):
+        _seed(memory, f"s{k}", 4)
+
+    # A backend hiccup in the consolidation rebuild must not abort the whole pass
+    # (this is what broke the cycle when the MI50 was down).
+    monkeypatch.setattr(profile, "rebuild_profile",
+                        lambda *a, **k: (_ for _ in ()).throw(RuntimeError("backend down")))
+
+    state = dream.dream_cycle(force=True)
+    acts = state["dream"]["last_actions"]
+
+    assert any("coherence" in a and "fail" in a for a in acts)  # logged, not fatal
+    assert any("reflected" in a for a in acts)                  # cycle still reached reflection