fix(settings): keep rename and selected models visible

[Blue-Berrys]

Problem

In three-column mode, Electron's native HTML preview could cover the session rename dialog. The provider editor also expanded the first selected model automatically, pushing the remaining checked model names below the fold and making the selection look blank.

Change

• Register the session rename dialog as a blocking overlay so the native preview is hidden for the dialog lifetime and restored after dismissal.
• Keep fetched and checkbox-selected model rows collapsed until Advanced is explicitly opened, so all selected model IDs remain visible.
• Extend the mounted production-component Electron regression fixture and the E2E specification for both behaviors.

Relates to #904.

Validation

• node --test apps/desktop/test/session-rename.test.mjs apps/desktop/test/provider-model-config.test.mjs apps/desktop/test/model-advanced-capabilities.test.mjs — 44 passed
• PI_DIALOG_ARTIFACT_DIR=/tmp/pi904-fixed node scripts/test-dialog-overflow.mjs — 36 passed, including native-preview suppression and four visible selected model rows
• Desktop TypeScript check passed
• electron-vite build passed
• Full desktop test sweep reached 2,652 passing tests; the five tests that initially lacked generated workspace dist artifacts were rebuilt and rerun separately — 32 passed

[vastsa]

感谢 pr，我正在重新设计模型这块页面，现在交互越来越麻烦，用户心智要求越来越高