[ENHANCEMENT] Add Sonnet 4.5 1M Model to Claude Code Provider

[ColbySerpa]

Problem (one or two sentences)

This request was discussed on Discord. @mrubens told me to make a PR. First, I have to make an approved issue. This is the issue. The PR will add the model and link to this issue.

Context (who is affected and when)

Anyone who uses Claude Code instead of API.

Desired behavior (conceptual, not technical)

Adding a new model to Claude Code that has a 1M context window.

Constraints / preferences (optional)

No response

Request checklist

• I've searched existing Issues and Discussions for duplicates
• This describes a specific problem with clear context and impact

Roo Code Task Links (optional)

No response

Acceptance criteria (optional)

No response

Proposed approach (optional)

No response

Trade-offs / risks (optional)

No response

[roomote]

I'm exploring a potential fix for adding the Sonnet 4.5 1M model to the Claude Code Provider and will open a PR to share progress.

[roomote]

Opened PR #8587 with my attempt at addressing this issue. All CI checks are passing. The implementation adds the claude-sonnet-4-5-1m model variant with 1M context window to the Claude Code provider. Feedback welcome!