docs: document Inception Mercury models

[Fental]

Summary

• Replace the generic Inception config placeholders with a concrete mercury-2 example.
• Add an available models table for mercury-2, mercury-edit-2, and mercury-coder-small.
• Document context length and recommended usage for each model.
• Note that mercury-2 supports tool calling in Continue.

Related issue

Closes #12466

Test plan

• Verified model names and context lengths against packages/llm-info/src/providers/inception.ts.
• Verified mercury-2 tool calling support against core/llm/toolSupport.ts.
• Ran a lightweight docs check confirming the model names, context length, and tool calling note are present.

🤖 Generated with Claude Code

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Summary by cubic

Update the Inception provider docs with a concrete mercury-2 config example and a models table for mercury-2, mercury-edit-2, and mercury-coder-small, including context limits and recommended uses. Also note that mercury-2 supports tool calling in Continue.

^{Written for commit c6b7ac4. Summary will update on new commits. Review in cubic}

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[cubic-dev-ai]

No issues found across 1 file

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[Fental]

I have read the CLA Document and I hereby sign the CLA

[Fental]

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