[Revert] Router lookup gate and Gemini routing default (#716)

[daniel-lxs]

Reverts #716 (squash a3d7978) after routing degraded in production: a plain "Review the README in the Roomote repo" request fell through to the manual environment picker instead of routing confidently.

Restores the pre-#716 behavior: unconditional issue fetch from #693 and routing on the deployment small model (R_SMALL_MODEL). #718's registry refactor is untouched (no file overlap) and #722 stays unmerged.

Leading theory (debugging in parallel): the google/gemini-3.6-flash default doesn't resolve through the deployment's OpenCode provider config (splitOpenCodeModelId → provider google, which may not be registered — the eval validated the model via OpenRouter directly, not through the production provider path). If confirmed, the model call throws, routeTask catches, and every route degrades to fallback → manual picker, which matches the screenshot.

🤖 Generated with Claude Code

[roomote-roomote]

No code issues found. See task

_{Reviewed b92bf3d}