ADFA-6303 | Add Semantic Search settings screen to Vector Search

[jatezzz]

Description

Until now the embedding model could only be set in each AI provider's own settings, and when a provider couldn't do search, Vector Search showed an error with no fix. Users also couldn't see which provider and model search used, what had been indexed, or that indexing sends their code to the provider. This adds a Vector Search settings screen that shows all of that, lets users pick the embedding model, and lets them clear the index.

Technical implementation:

• New SemanticSearchSettingsFragment/ViewModel shows whether the selected backend works with search, the embedding-model picker, a privacy line, index status, build history, and Clear index with a confirmation dialog. BackendWatch refreshes the screen whenever the backend or model changes.
• Gemini and OpenAI now implement EmbeddingModelSelectable (listEmbeddingModels/setEmbeddingModelId), and their settings panes no longer show the embedding model. A value saved there before the upgrade is the one the new screen preselects.
• IndexCoordinator runs index builds and clears one at a time, so a clear during a build can't leave a partial or mixed-model index. The SQL was split out into EmbeddingsSql.
• Tooltips and the Tier 3 docs cover the new screen. min_ide_version is 26.41 for Vector-Search, AI-Agent-Gemini and AI-Agent-OpenAI.

Details

Demo:

https://drive.google.com/file/d/1At3aZZe65Xrfg8Pz3e1AZjp_mCbx89By/view?usp=sharing

Ticket

ADFA-6303
Relates to: ADFA-6277

Observation

Dependency: Stacked on feat/ADFA-6279-agent-capability-tags (ADFA-6279); needs CoGo 26.41's plugin-api (EmbeddingModelSelectable).

[Daniel-ADFA]

Review of ADFA-6303 at 8ef6f88 (top of its stack; base is feat/ADFA-6279-agent-capability-tags, no PR stacked above).

IMPORTANT

• IndexCoordinator.kt:133 - a superseding build can run concurrently with a pending clear and end up with a partial index
• SemanticSearchSettingsViewModel.kt:209 - Clear index is disabled in the Build failed state, the one state whose message tells the user to clear
• SemanticSearchSettingsFragment.kt:187 - a pick-only picker removes the free-text escape hatch the OpenAI embedding filter depends on

MINOR

• GeminiSettingsFragment.kt:764 (removed) - retired saved Gemini embedding models are no longer migrated

This repo has no written approve/request-changes rule, so the default severity table applied.

[Daniel-ADFA]

Reviewed at f915fd9; no correctness issues found.