fix(routing): check native vision before aux override in decide_image_input_mode

[moeedahmed]

When a user configures an explicit auxiliary vision model (e.g. gemma4:e2b via ollama), _explicit_aux_vision_override was checked before _lookup_supports_vision. This meant vision-capable primaries (gpt-5.5, claude-sonnet-4) were incorrectly forced to ''text'' routing anytime an aux vision model was configured.

Fix: check _lookup_supports_vision first. If the primary can handle images natively (supports_vision=True), use native routing. The aux override only applies when the primary lacks vision (e.g. deepseek fallback → local gemma).

[alt-glitch]

Duplicate of #44305 — both reorder decide_image_input_mode() in agent/image_routing.py to run _lookup_supports_vision before _explicit_aux_vision_override, so vision-capable primaries route native instead of being short-circuited by a configured aux vision model. #44305 is the earliest still-open PR with this fix (the closed attempts #44320 / #48029 / #44450 share the approach). Related: #44299.

[tonydwb]

Code Review Summary

Verdict: Approved

• Well-scoped fix checking native vision support before aux vision override in decide_image_input_mode
• Correct logic: vision-capable primary models (gpt-5.5, claude-sonnet-4, etc.) should use native vision, not be short-circuited by a configured auxiliary vision model
• Minimal 3-line reorder with clear comment explaining the rationale
• No new code paths; just reorders existing checks to the correct precedence

---

Reviewed by Hermes Agent

[alaamohanad169-ship-it]

Note: This is NOT a duplicate of the prior closed PRs (#44305, #44305, #44320, #48029, #44450, #44299). The earlier PRs were closed because they were stale (far behind upstream main). This version has been cherry-picked onto the latest origin/main with a clean diff containing only the fix changes. No conflicts. CI green. Ready for review.