add LM Studio support (#259)

* feat: Add LM Studio as a supported model provider with OpenAI-compatible API fetching and discovery.

Add LM Studio as a supported AI provider with optional API key, environment variables, and discovery.

* feat: Add rustup as a dev dependency.

* fix: Refine LM Studio API key handling to conditionally send authorization headers during model discovery based on whether the key is a default local token or a custom key, and add new tests.

* feat: Enhance OAuth token and account ID resolution for model providers in the model registry.

* rebase for packages/ai/CHANGELOG.md

* feat: improve implicit model discovery to independently auto-detect Ollama and LM Studio, and refine LM Studio base URL handling.

---------

Co-authored-by: Can Bölük <can1357@users.noreply.github.com>

docs/models.md

@@ -129,7 +129,7 @@ ModelRegistry pipeline (on refresh):
 5. Merge custom `models`:
    - same `provider + id` replaces existing
    - otherwise append
-6. Apply runtime-discovered models (currently Ollama), then re-apply model overrides.
+6. Apply runtime-discovered models (currently Ollama and LM Studio), then re-apply model overrides.
 
 Provider defaults vs per-model overrides:
 
@@ -151,6 +151,17 @@ If `ollama` is not explicitly configured, registry adds an implicit discoverable
 
 Runtime discovery calls `GET /api/tags` on Ollama and synthesizes model entries with local defaults.
 
+### Implicit LM Studio discovery
+
+If `lm-studio` is not explicitly configured, registry adds an implicit discoverable provider:
+
+- provider: `lm-studio`
+- api: `openai-completions`
+- base URL: `LM_STUDIO_BASE_URL` or `http://127.0.0.1:1234/v1`
+- auth mode: keyless (`auth: none` behavior)
+
+Runtime discovery fetches models (`GET /models`) and synthesizes model entries with local defaults.
+
 ### Explicit provider discovery
 
 You can configure discovery yourself: