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

lyra/dream.py

@@ -124,11 +124,18 @@ def dream_cycle(backend: Backend | None = None, force: bool = False) -> dict:
 
     # --- coherence: fold gists up into profile / eras / narrative ---
     if (force or drives["coherence"] >= THRESHOLD) and not _over_budget(deadline):
-        profile.rebuild_profile(backend=backend)
-        era.rebuild_eras(backend=backend)
-        narrative.rebuild_narrative(backend=backend)
-        actions.append("integrated knowledge (profile/eras/narrative)")
-        drives["coherence"] = 0.0
+        # A backend hiccup here must not sink the whole pass (reflection still
+        # deserves to run); log it and move on, leaving coherence unrelieved so a
+        # later cycle retries.
+        try:
+            profile.rebuild_profile(backend=backend)
+            era.rebuild_eras(backend=backend)
+            narrative.rebuild_narrative(backend=backend)
+            actions.append("integrated knowledge (profile/eras/narrative)")
+            drives["coherence"] = 0.0
+        except Exception as exc:
+            logbus.log("error", "coherence stage failed", error=str(exc)[:200])
+            actions.append("coherence stage failed")
         # Off-hot-path villain identity housekeeping: propose likely same-person
         # merges for Brian to confirm on the Players page. Never sinks the cycle.
         try: