[Fix] Anthropic Opus 4.7 fails when reasoning is enabled

[roomote]

Opened on behalf of Elliott de Launay. View the task or mention @roomote for follow-up asks.

What problem this solves

Fixes an issue where users hitting the direct Anthropic provider with claude-opus-4-7 would get a 400 error once reasoning was enabled, because Zoo Code still sent the legacy budget-based thinking payload that Opus 4.7 rejects.

Why this change was made

This switches the direct Anthropic Opus 4.7 path to an adaptive reasoning payload and updates the model metadata so the UI treats reasoning as a binary toggle for that provider/model combination. It also strengthens regression coverage at both the provider layer and the VS Code e2e boundary so the outbound request shape is checked directly.

User impact

Anthropic Opus 4.7 reasoning requests now use the payload the provider expects, so enabling reasoning no longer trips the "thinking.type.enabled" request error on that path. The updated e2e also guards the extension-host wiring so future changes are less likely to regress this again.

[roomote]

1 issue outstanding. Action required. See task

• The Opus 4.7 max-token regression from the initial capability change was addressed on the latest head.
• The Anthropic proxy helper now constrains the upstream target and returns a generic failure response, so the earlier CodeQL alerts are addressed on the latest head.
• After the 10-minute wait cap, 1 CI check is still pending on ed45057: platform-unit-test (ubuntu-latest). — dismissed: superseded by the newer head 8a1884c, which reran CI.
• After the wait window, platform-unit-test (ubuntu-latest) is still pending on 8a1884c. — dismissed: rerun on the newer head f7bf252 passed after the current 10-minute wait window.
• After the wait window, platform-unit-test (windows-latest) is still pending on 8a1884c. — dismissed: superseded by the newer head f7bf252, which reran CI.
• After the 10-minute wait cap, platform-unit-test (windows-latest) is still pending on f7bf252.

[codecov]

Codecov Report

❌ Patch coverage is 83.92857% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/api/providers/anthropic.ts	78.04%	9 Missing ⚠️

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