feat: add image recognition model auto-switching

[OHCJ099]

This PR implements model auto-switching for image recognition/vision tasks.

Features:

1. Auto-Switching Model: Dynamically switches the model to \mimo-v2-omni\ (or the configured vision model) when the current turn contains an image (including pasted/uploaded images inside file attachments).
2. History Sanitization: Replaces image content blocks and image attachments in previous turns with placeholder text, allowing text-only models (like \mimo-v2.5-pro) to proceed on subsequent turns without API validation errors.
3. Custom Configuration: Users can customize their preferred vision model and switch preferences using the \imageRecognition\ block in \settings.json.

代码已测试无误，可以直接合入。

[github-actions]

PR quality triage

Changed areas: area:cli-core, area:desktop

CLI core policy: Blocked by policy until a maintainer applies allow-cli-core-change and approves the PR.

Missing-test policy: Blocked by policy until a maintainer applies allow-missing-tests or matching tests are added.

Coverage baseline policy: No coverage-baseline policy block detected.

CLI core files:

• src/utils/settings/types.ts

Coverage policy files:

• none

Expected checks:

• change-policy
• desktop-checks
• server-checks
• desktop-native-checks
• coverage-checks

Test coverage signals:

• BLOCKING unless allow-missing-tests is applied: Agent/runtime product files changed without a tools/utils test file in the PR.
• Agent/model runtime path changed: use mock/request-shape tests in PR and maintainer live-model smoke before release.

Risk notes:

• No special risk notes from changed paths.

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