feat(chat): surface missing-model discovery errors as AgentStartupError

[tudormatei1]

What & why

When a model name isn't returned by the discovery API, get_model_info raises ModelNotFoundError. Until now get_chat_model let it propagate raw, so the runtime showed an opaque exception instead of an actionable message.

This PR catches ModelNotFoundError and re-raises it as a structured AgentStartupError (code LLM_INVALID_MODEL, category DEPLOYMENT). If a byo_connection_id is set, the message points to the connection's bring-your-own-model config; otherwise it asks you to check the model name and tenant enablement. The original error is preserved as __cause__.

Changes

• chat/chat_model_factory.py: maps ModelNotFoundError to AgentStartupError. AgentStartupError / UiPathErrorCategory imported lazily inside the except block to avoid a chat -> agent import cycle.
• pyproject.toml: uipath-llm-client / uipath-langchain-client floors to >=1.17.1,<1.18.0; version to 0.14.11.
• uv.lock: regenerated (resolves 1.17.1).
• Tests: TestGetChatModelModelNotFound covers the mapping, BYO variant, and __cause__ chain.

Depends on

uipath-llm-client 1.17.1 (adds ModelNotFoundError + UiPathLLMErrorCode.MODEL_NOT_FOUND). Already published.

[Copilot]

Pull request overview

This PR improves startup-time error reporting for LLM configuration by converting “model not found in discovery” failures into a structured AgentStartupError (LLM_INVALID_MODEL, category DEPLOYMENT). This aligns the chat-model dispatcher with the agent runtime’s structured error surface so deployments get actionable, user-facing guidance instead of an opaque exception.

Changes:

• Catch ModelNotFoundError in chat_model_factory.get_chat_model() and re-raise as AgentStartupError, preserving the original exception as __cause__ and tailoring the detail message for BYO connections.
• Bump uipath-llm-client / uipath-langchain-client floors to >=1.17.1,<1.18.0 and version the package to 0.14.11.
• Add tests covering the mapping behavior, BYO detail variant, and cause chaining.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
src/uipath_langchain/chat/chat_model_factory.py	Maps discovery “missing model” failures to structured startup errors with actionable guidance (including BYO connection messaging) and preserved __cause__.
tests/chat/test_chat_model_factory.py	Adds coverage for the error mapping behavior, BYO detail inclusion, and exception cause chaining.
pyproject.toml	Updates package version and floors client dependencies to include the new ModelNotFoundError.
uv.lock	Regenerates lockfile reflecting the dependency/version bumps.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud