ADFA-6119 | Unify AI settings panes and fix dropdown chevrons

[jatezzz]

Description

This PR unifies the visual design of the AI settings panes and fixes an issue where dropdown chevrons were missing due to a Material 1.10 XML limitation. By adopting shared plugin styles and replacing the legacy Gemini spinner, both backends now offer a consistent, interactive, and intuitive user experience.

• Fixed the missing dropdown chevron on the OpenAI server preset and model fields.
• Replaced the Gemini model picker Spinner with a TextInputLayout plus AutoCompleteTextView to match the OpenAI control.
• Applied ic_dropdown programmatically via setEndIconDrawable() to bypass a Material 1.10 limitation where endIconMode="custom" fails to read the XML drawable.
• Removed the "Current: X" label from the Gemini pane, as the text field itself now displays the active model.
• Standardized the Gemini pane's buttons, labels, and margins using shared plugin styles like PluginButton.Filled, Plugin.SectionHeader, and shared space_* dimensions.
• Ensured the Gemini model picker remains pick-only because its catalog is closed and there is no free-text model to type.
• Unified the panes so users can visually recognize the interactive dropdown menus and experience a consistent IDE interface across AI backends.

Details

Before

Before.ADFA-6119.mp4

After

After.ADFA-6119.mp4

Ticket

ADFA-6119

[claude]

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[Daniel-ADFA]

MINOR

• GeminiSettingsFragment.kt:586 - the "Material 1.10 never reads app:endIconDrawable" explanation is wrong (the same claim appears in four places)
• fragment_gemini_settings.xml:143 - maxLines="1" probably clips long model names at font scale 2.0 (not checked on a device)

NITPICK - 1 inline, not listed

The core change holds up: the dropdown uses the non-filtering setText(..., false) everywhere, the field is pick-only, and it doesn't save or restore its own text, so the list isn't filtered down to the selected entry after a day/night switch. setupDropdownEndIcon runs before both end-icon listeners are attached, so a mode reset can't wipe them. Migrating off a retired model is still limited to live catalogs. The dispose() change in OpenAI matches what GeminiPlugin already does.

This repo has no written approve/request-changes rule, so the default applied: only MINOR findings, so this is a comment rather than approval or request for changes. No earlier review findings to re-check. Reviewed at 1a10999.

[Daniel-ADFA]

Approving: the two MINOR comments are fine as follow-ups. Please fix the endIconDrawable explanation and check the model field at font scale 2.0 before the next change to these panes.