tui: exit session on Ctrl+C in cwd change prompt

[charley-oai]

Summary

• change the cwd-change prompt (shown when resuming/forking across different directories) so Ctrl+C/Ctrl+D exits the session instead of implicitly selecting "Use session directory"
• introduce explicit prompt and resolver exit outcomes so this intent is propagated cleanly through both startup resume/fork and in-app /resume flows
• add a unit test that verifies Ctrl+C exits rather than selecting an option

Why

Previously, pressing Ctrl+C on this prompt silently picked one of the options, which made it hard to abort. This aligns the prompt with the expected quit behavior.

Codex author

codex resume 019c6d39-bbfb-7dc3-8008-1388a054e86d

[charley-oai]

@codex review this

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Another round soon, please!

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