Stream model responses and tool progress in the terminal

[Xsoleils]

Problem

Long coding tasks currently feel quiet between model selections and completed tool calls. Users need earlier feedback without exposing raw provider protocol data or making the persistent terminal header unstable.

Proposed experience

Add end-to-end streaming for providers that support it, with a safe non-streaming fallback.

Acceptance criteria:

• Extend the adapter contract with typed text/tool progress events.
• Render incremental assistant text without breaking the full-screen header or approval prompts.
• Keep complete tool arguments hidden until they are validated.
• Preserve Ctrl+C cancellation and existing headless JSON output.
• Add adapter and UI tests for streamed text, interrupted streams, and fallback behavior.
• Never stream credentials, request headers, or raw secret-file contents.

Free-first policy

• This proposal preserves SoleilCode's free-first and approval-by-default principles.