fix(omniroute): raise REQUEST_TIMEOUT_MS and enable --cache-reuse to stop non-ping SSE stream aborts

STREAM_IDLE_TIMEOUT_MS was raised to 180s on 2026-09-09 to give contended
llama-server prefill room to produce a first token, but qwen-code sessions
kept hitting "Stream produced no non-ping SSE event within 95000ms" the very
next morning. Per OmniRoute's own docs, that's the wrong timer: the first
non-ping SSE event's deadline inherits REQUEST_TIMEOUT_MS (default 10 min,
computed as remaining budget after retries/cooldowns), not
STREAM_IDLE_TIMEOUT_MS (which only bounds gaps between chunks once streaming
has already started).

Two changes:
- Add REQUEST_TIMEOUT_MS=1800000 (30 min) on the omniroute service, exposed
  as OMNIROUTE_REQUEST_TIMEOUT_MS like the existing stream-idle var. Safety
  margin, not the root-cause fix.
- Add --cache-reuse 256 to llama-server: it had no KV-cache reuse configured,
  so every request reprefilled its full prompt from scratch even when most
  of a conversation's prefix was unchanged. This is the actual fix for why
  compact-prompt prefill was slow enough to hit the timeout in the first
  place.

Documents the distinction and root cause in docs/research/.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WqWBahogLCkrXNfzCSvcVc

docker-compose.yml

@@ -30,7 +30,16 @@ services:
       --flash-attn on
       --cache-type-k q8_0
       --cache-type-v q8_0
+      --cache-reuse 256
       --jinja
+    # --cache-reuse 256: reuse cached KV for any matching prompt chunk of at
+    # least 256 tokens (KV-shift, no reprocessing) instead of reprefilling
+    # from scratch every request. Directly targets the actual root cause
+    # behind the OmniRoute non-ping SSE timeout, not just the symptom — see
+    # docs/research/omniroute-non-ping-sse-stream-timeout.md. Pairs with
+    # OmniRoute's promptCacheAffinityEnabled (dashboard default), which keeps
+    # a conversation's requests pinned to the same slot so there's a matching
+    # prefix to reuse.
     # No published host port: llama-server is reached only via the omniroute
     # gateway on the ai-stack docker network now — see issue #15. Its
     # unauthenticated API no longer needs to be LAN-reachable directly.
@@ -283,6 +292,16 @@ services:
       # LLAMA_PARALLEL above for the other half of this fix). Raised here so
       # it's tracked in git instead of a dashboard-only setting.
       - STREAM_IDLE_TIMEOUT_MS=${OMNIROUTE_STREAM_IDLE_TIMEOUT_MS:-180000}
+      # Different timer than STREAM_IDLE_TIMEOUT_MS above — that one only
+      # bounds gaps *between* SSE chunks once streaming has started.
+      # REQUEST_TIMEOUT_MS bounds the wait for the *first* non-ping SSE
+      # event, and it's what was still firing ("Stream produced no non-ping
+      # SSE event within 95000ms") the morning after the timeout above was
+      # raised — see docs/research/omniroute-non-ping-sse-stream-timeout.md.
+      # Default 600000 (10 min) per OmniRoute's own docs, but the effective
+      # deadline is remaining budget after retries/cooldowns eat into it, not
+      # a flat timer, so raised well past the default for headroom.
+      - REQUEST_TIMEOUT_MS=${OMNIROUTE_REQUEST_TIMEOUT_MS:-1800000}
     # Same reasoning as litellm's extra_hosts entry below — ai-stack's bridge
     # network can't resolve search.home on its own.
     extra_hosts: