[Feature Request] Add support for model selection and prompt injection within conversations

Bug Description
It would be nice to be able to separate models and provide prompts within a conversation.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.86
• Feedback ID: 518e7622-0357-4793-85a4-e0d8872163b6

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/gimdong-ug/.local/share/claude/versions/2.1.86 (expected in multi-process scenarios)\n    at _p_ (/$bunfs/root/src/entrypoints/cli.js:2851:2138)\n    at Vn6 (/$bunfs/root/src/entrypoints/cli.js:2851:1218)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-28T16:33:51.934Z"},{"error":"Error: Failed to fetch version from https://storage.googleapis.com/claude-code-dist-86c565f3-f756-42ad-8dfa-d59b1c096819/claude-code-releases/latest: ECONNREFUSED\n    at Ub1 (/$bunfs/root/src/entrypoints/cli.js:2849:14863)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-29T02:11:33.626Z"},{"error":"Error: Failed to fetch version from https://storage.googleapis.com/claude-code-dist-86c565f3-f756-42ad-8dfa-d59b1c096819/claude-code-releases/latest: ECONNREFUSED\n    at Ub1 (/$bunfs/root/src/entrypoints/cli.js:2849:14863)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-29T02:11:33.635Z"}]

]