fix: correct Gemini 3 pricing for Flash and Pro models

[roomote]

Related GitHub Issue

Closes: #10432

Description

This PR attempts to address Issue #10432 by correcting the pricing for Gemini 3 Flash and Pro models in both Gemini and Vertex providers.

Changes made:

gemini-3-flash-preview:

• inputPrice: 0.3 -> 0.5
• outputPrice: 2.5 -> 3.0
• cacheReadsPrice: 0.075 -> 0.05
• cacheWritesPrice: 1.0 -> 0.0

gemini-3-pro-preview:

• Added tiered cacheReadsPrice: 0.2 (<=200k tokens) and 0.4 (>200k tokens)
• Added cacheWritesPrice: 0.0

The pricing now matches the official Google API pricing documentation at https://ai.google.dev/gemini-api/docs/pricing

Test Procedure

• Verified the build passes (pnpm --filter @roo-code/types build)
• Type checking passed
• Linting passed

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue.
• Scope: Changes are focused on the linked issue (pricing fix only).
• Self-Review: I have performed a thorough self-review of the code.
• Testing: These are configuration changes (pricing values) - no new tests needed.
• Documentation Impact: No documentation updates required.
• Contribution Guidelines: I have read and agree to the Contributor Guidelines.

Documentation Updates

• No documentation updates are required.

Additional Notes

Feedback and guidance are welcome.

[roomote]

Rooviewer   See task on Roo Cloud

Review complete. No issues found.

The removal of cacheWritesPrice: 0.0 from gemini-3-pro-preview and gemini-3-flash-preview follows the maintainer's guidance. Changes are consistent between gemini.ts and vertex.ts.

Previous reviews

• 19abd30: Review #1

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[hannesrudolph]

@roomote I don't think we need cacheWritesPrice: 0.0 since the write price would be the same as the input price.

[hannesrudolph]

@roomote We also need to address the gemini-3-pro-preview pricing

[roomote]

Fixaroo   See task on Roo Cloud

Removed cacheWritesPrice: 0.0 from Gemini 3 Flash and Pro models in both gemini.ts and vertex.ts. All local checks passed.

_{View commit | Revert commit}

[roomote]

Fixaroo   Follow along on Roo Cloud

I've verified the current gemini-3-pro-preview pricing implementation:

Cache pricing (matches issue #10432):

• cacheReadsPrice: $0.20 (<=200k tokens), $0.40 (>200k tokens) ✓
• cacheWritesPrice: $0.00 ✓

Current input/output pricing:

• Input: $2.00 (<=200k) / $4.00 (>200k)
• Output: $12.00 (<=200k) / $18.00 (>200k)

Build and lint checks pass. I'm unable to view the attached image directly. If the input/output prices shown in the image differ from the current values, please share them in text form and I'll update them right away.