Refactor the cherry-picked #40338 backend half:
- Move option merging from import-time _SCHEMA_OVERRIDES mutation to a
per-request overlay in GET /api/config/schema — options now reflect the
current config.yaml (no restart needed) and the module-level
CONFIG_SCHEMA is never mutated. The endpoint gains an optional
?profile= param scoped via _config_profile_scope.
- Keep builtin display order first, customs appended (drop the
sorted(set(...)) re-sort) — matches desktop enumOptionsFor.
- Only command-type provider blocks count (type absent or 'command' plus
non-empty command string), enumerated from the canonical
<kind>.providers.* location AND the legacy top-level <kind>.<name>
fallback — the same dual resolution as _get_named_provider_config /
_get_named_stt_provider_config. Builtin-name collisions are excluded
case-insensitively against the RUNTIME builtin sets (not the display
shortlist), mirroring apps/desktop/src/app/settings/helpers.ts
commandProviderNames (#67209).
- Drop the plugin.yaml 'provides: [tts]' manifest scan — that convention
does not exist (manifests carry provides_tools/provides_hooks only);
plugin TTS/STT providers register at runtime via
ctx.register_tts_provider(). Instead, opportunistically include names
from agent.tts_registry / agent.transcription_registry when plugins
happen to be loaded in this process.
- Current tts.provider/stt.provider value preserved in options.
- Tests: custom command provider merge (tts+stt), builtin-order
preservation, EDGE collision exclusion, non-command block exclusion,
current-value preservation, per-request freshness, legacy top-level
block support.
