fix: cap MI50 summary length + fast-fail cloud fallback

The dream cycle's summarize_all ran uncapped against the MI50: no max_tokens
and no timeout, so the OpenAI SDK's 600s x2-retry default meant ~30 min per
call. Combined with summary.py's own retry loop, one unsummarizable session
pegged the GPU for hours (observed 2026-07-04: stuck since 23:02, nothing saved
since 00:56, 7-8k-token runaway generations, all 4 llama.cpp slots busy). Not
context overflow (0 shifts/truncations) - purely unbounded length on a slow
backend timing out and retrying.

- llm.complete(): add optional max_tokens (caps generation; num_predict for
  Ollama) and timeout (bounds the request and sets max_retries=0 so the caller
  owns retry policy). Both default None -> unchanged for every existing caller.
- summary.py: cap gists at 768 tokens, 150s/call fast-fail, 2 MI50 attempts
  then one cloud fallback (when primary isn't already cloud and a key exists).

Known limitation (scoped out per decision): the fallback triggers on
timeouts/exceptions, not on a degraded backend returning garbage as a 200.

Tests: fallback fires after 2 MI50 failures; no fallback when primary is cloud
or no key; cap+timeout threaded into every complete() call; llm bounds tests.
172 pass, ruff clean.

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

lyra/summary.py

@@ -17,7 +17,16 @@ from concurrent.futures import ThreadPoolExecutor, as_completed
 from lyra import config, llm, logbus, memory
 from lyra.llm import Backend, Message
 
-_RETRIES = 4
+# Consolidation LLM budget. A gist is short (a handful of sentences), so cap the
+# generation hard — an uncapped local model will otherwise ramble for thousands
+# of tokens and, on a slow GPU, blow the request timeout. 768 is ~3x the longest
+# real gist we've stored.
+SUMMARY_MAX_TOKENS = 768
+# Attempts on the primary backend before falling back to cloud.
+MI50_ATTEMPTS = 2
+# Per-call timeout (seconds). A capped 768-token gist finishes in ~60-90s on the
+# MI50; 150s is headroom but bails a hung call fast so fallback isn't slow.
+SUMMARY_TIMEOUT = 150
 
 # Re-summarize a session once it has accumulated this many new raw exchanges.
 SUMMARIZE_AFTER = 20
@@ -61,16 +70,32 @@ def _summarize_text(text: str, backend: Backend) -> str:
         {"role": "system", "content": _PROMPT},
         {"role": "user", "content": text},
     ]
-    # Retry transient backend errors (e.g. the GPU server restarting) with backoff.
-    for attempt in range(_RETRIES):
+
+    def _call(be: Backend) -> str:
+        return llm.complete(messages, backend=be,
+                            max_tokens=SUMMARY_MAX_TOKENS, timeout=SUMMARY_TIMEOUT)
+
+    # Try the primary backend a bounded number of times (each call fast-fails via
+    # SUMMARY_TIMEOUT), with a short backoff for a transient blip / restarting GPU.
+    last_exc: Exception | None = None
+    for attempt in range(MI50_ATTEMPTS):
         try:
-            return llm.complete(messages, backend=backend)
+            return _call(backend)
         except Exception as exc:
-            if attempt == _RETRIES - 1:
-                raise
-            logbus.log("debug", "summary retry", attempt=attempt + 1, error=str(exc)[:80])
-            time.sleep(5 * (attempt + 1))
-    raise RuntimeError("unreachable")
+            last_exc = exc
+            logbus.log("debug", "summary retry", attempt=attempt + 1,
+                       backend=backend, error=str(exc)[:80])
+            if attempt < MI50_ATTEMPTS - 1:
+                time.sleep(5 * (attempt + 1))
+
+    # Primary exhausted. If it wasn't already cloud and cloud is configured, fall
+    # back once so a stuck/offline MI50 doesn't sink consolidation for the night.
+    if backend != "cloud" and config.load().openai_api_key:
+        logbus.log("info", "summary fell back to cloud", primary=backend,
+                   error=str(last_exc)[:80] if last_exc else None)
+        return _call("cloud")
+
+    raise last_exc if last_exc else RuntimeError("summary failed")
 
 
 def _summarize_transcript(transcript: str, backend: Backend) -> str: