Add OpenAI and Anthropic provider adapters #40

Goal

Support the two native cloud-provider families through the provider contract.

Depends on

• Define a provider-neutral AI client and capability contract #35, Move AI execution and credentials into a secure Electron main-process service #36, Add provider profiles and connection controls to Settings #37, and Migrate LM Studio to the provider abstraction without behavior regressions #38.

Scope

• Add OpenAI and Anthropic adapters.
• Map Lucid lane settings without assuming identical provider parameters.
• Support streaming, cancellation, model selection, structured output, usage reporting, and sanitized errors where available.
• Keep provider-specific translation inside adapters.

Acceptance criteria

• Input, Command, and Advisor can be exercised against both providers.
• Unsupported controls are omitted rather than guessed.
• Command safety behavior is covered by adapter contract tests.
• API keys never leave the main process after submission.