* fix: respect disabled auto-compaction on context overflow
Port from anomalyco/opencode#30749.
When compression.enabled is false, NO automatic compaction trigger may
fire. The proactive token-threshold paths (preflight + post-response
should_compress gate) already honoured the setting, but the three
provider-overflow recovery paths in the agent loop — long-context-tier
429, 413 payload-too-large, and context-overflow — called
_compress_context() unconditionally, silently compressing and rotating
the session against the user's explicit choice.
Add a single guard at the top of the overflow-recovery dispatch: when
compression is disabled and the error is one of those three overflow
classes, surface a terminal error (compaction_disabled: True) telling the
user to /compress manually, /new, switch to a larger-context model, or
reduce attachments. Manual /compress (force=True) is unaffected — it never
enters this loop.
Tests: new TestOverflowWithCompactionDisabled (413 + 400 overflow don't
compress when disabled; control case still compresses when enabled).
Existing overflow-recovery tests updated to enable compaction explicitly
(they verify the recovery fires); fixture defaults flipped to True to
match production (compression.enabled defaults to True).
* perf(/model): prewarm picker provider-models cache in background
The no-args /model picker calls list_authenticated_providers(), which
fetches each authenticated provider's live /v1/models list serially. On a
cold or stale (>1h TTL) cache that blocks ~1.5s on the user's critical path
the first time /model is opened in a session.
Warm that exact path off-thread during the idle window right after the CLI
banner is shown: a once-per-process daemon thread runs
list_authenticated_providers() to populate provider_models_cache.json for
every authed provider. By the time the user types /model, the picker hits
the warm disk cache (~136ms vs ~1500ms).
Process-level Event guard (mirrors run_agent's _openrouter_prewarm_done)
ensures at most one thread per process; fully exception-isolated so an
offline/no-creds provider can never affect the session.
