ADFA-5096 | Split the AI backends into standalone plugins

[jatezzz]

Description

Reshapes the AI plugin set from ai-core + ai-assistant into one agent plugin plus one plugin per inference backend, so a user installs only the engine they want and a new backend can ship without touching this repo.

• ai-core — the Agent chat (tool layer, view models, UI, all folded in from ai-assistant, which is deleted) plus the LlmInferenceService router. Ships no model; discovers installed engines through BackendRegistry and names no provider anywhere in its code.
• ai-agent-llm — on-device .gguf backend (bundled llama.cpp AAR, native.code), registers as local.
• ai-agent-gemini — Gemini API backend (network.access), registers as gemini.

Along the way: each backend owns its preferences instead of reading ai-core's AgentSettings; each contributes its own settings pane, system prompt and tests; the ADFA-5095 LlmBackend split is adopted (getConfigSpecs/settingsFragmentClassName moved onto ConfigurableBackend, supportsHistory declared, backend closed on deactivate() so disabling no longer orphans a live instance); and every plugin's sources are laid out by layer (plugin/, backend/, preferences/, services/, logging/…) with utils/ and data/ gone and logs tagged per plugin.

Because plugins load in parallel with no ordering guarantee, settings had to stop depending on who activated first. Each backend now reads the host's legacy store directly and migrates once from every prior location (old plugin id from before the ai-backend-* → ai-agent-* rename, ai-core, ai-assistant, the host's LlamaPrefs), guarded by a migrated_* flag so a value changed since is never clobbered. A device configured on the old build stays configured.

Details

7 commits, 233 files, mostly moves/renames:

ai-assistant/	deleted — merged into ai-core
ai-backend-local/ → ai-agent-llm/	folder, package, plugin.id, label (submodule path in .gitmodules follows)
ai-backend-gemini/ → ai-agent-gemini/	folder, package, plugin.id, label

Plugin ids after the rename: …plugins.aicore, …plugins.aiagentllm, …plugins.aiagentgemini. README's examples table rewritten to state the new dependency shape (AI Core is mandatory; install at least one backend).

Tests moved with the code they cover and now sit under each owning plugin — 31 test files across the three plugins, all passing.

document_5179206860728698887.mp4

Ticket

ADFA-5096

[claude]

Claude Code Review

This repository is configured for manual code reviews. Comment @claude review for a one-time review, or @claude review always to subscribe this PR to a review on every future push.

_{Tip: disable this comment in your organization's Code Review settings.}

[hal-eisen-adfa]

This depends on appdevforall/CodeOnTheGo#1660 landing first