feat(cohere): add support from Reasoning/Vision/Translate models

[maxbrunet]

Description

[ What changed? Feel free to be brief. ]

• Add support for reasoning in Cohere provider
• Add reasoning/vision models
• Add translate models (I was a bit hesitant, but I thought working on i18n of an app could be a good use case, and there is no particular extra work to support it)
• Add basic tests for Cohere provider

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Checklist

• [x] I've read the contributing guide
• [x] The relevant docs, if any, have been updated or created
• [x] The relevant tests, if any, have been updated or created

Screen recording or screenshot

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Tests

[ What tests were added or updated to ensure the changes work as expected? ]

• Update toolSupport tests for vision model
• Add basic tests for Cohere provider

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Summary by cubic

Add Cohere Reasoning, Vision, and Translate model support across the provider, UI, and docs. Enables thinking traces, image input, and new models with correct tool-calling behavior and tests.

• New Features
  • Reasoning: handle thinking content (stream/non-stream), configurable token_budget, and autodetect for command-a-reasoning models.
  • Vision: accept image_url inputs; disable tool use for command-a-vision models.
  • Translate: add command-a-translate model.
  • Message shaping: merge thinking with assistant messages and support tool_calls correctly.
  • Ecosystem updates: VS Code schema, GUI model picker, llm-info metadata, and docs capability matrix.
  • Tests: add comprehensive Cohere provider tests and tool support tests.

^{Written for commit b7f0f42c22a0460f8e6f3f94bb38dac507edf63a. Summary will update automatically on new commits.}