fix(antigravity): refresh the model manifest so older Gemini models fold as legacy - #9397

💭 I want to check the changed files in scope - AntigravityDriver.ts and ModelManifest.ts, excluding the test file. Let me pull up the relevant code to see what's happening there.

1. browse_code — apps/server/src/provider/ModelManifest.ts

2. browse_code — apps/server/src/provider/Drivers/AntigravityDriver.ts

💭 I'm reviewing the changed lines against Effect conventions—checking that the new manifestUpdatedAtMs helper and exported encodeManifestCache are properly scoped, and whether exporting the latter just for tests conflicts with existing convention rules, which don't explicitly address that case. I'm also verifying AntigravityDriver correctly acquires modelManifest via namespace import and uses it consistently. So far nothing here looks like an actual convention violation—the comparison logic is a behavior change with tests already added, and no lint disables or scope-creep are present.

3. browse_code — apps/server/src/provider/Drivers/AntigravityDriver.ts

💭 Everything conforms here, no violations found. I'll call complete_check with a summary of "All clear" since there's nothing to report.