Fix login URL handling, add Ctrl+C support, add logout command

[matthiaswenz]

Summary

• Only use verification_uri: Never open verification_uri_complete — showing one URL but opening another is a phishing vector (an attacker who can tamper with the device auth response could set verification_uri_complete to a lookalike domain). Fixes regression from Use cleaner base URL in login output #728.
• Handle Ctrl+C: Make the "Press Enter to open..." prompt context-aware so Ctrl+C exits cleanly instead of leaving the process stuck on a blocking tty read
• Fix double-close bug: waitForEnter called tty.Close() on cancellation while a defer tty.Close() also ran on return — after the first close releases the FD, another goroutine could reuse that FD number and the deferred close would silently close an unrelated file
• Browser fallback URL: When the browser fails to open, print the approval URL so the user can copy-paste it
• Add entire logout: Removes stored credentials from the OS keyring, fully reversing entire login

Test plan

• Unit tests pass (mise run test:ci)
• Manual: run entire login, verify the same URL is shown and opened in browser
• Manual: run entire login, hit Ctrl+C at the prompt — verify clean exit
• Manual: run entire login with browser unavailable — verify URL is printed for copy-paste
• Manual: run entire logout — verify "Logged out." message and token removed from keyring

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[Copilot]

Pull request overview

Fixes entire login’s device-auth URL handling and interrupt behavior, and adds a logout command to remove stored credentials from the keyring.

Changes:

• Print the clean verification_uri but open verification_uri_complete in the browser during login.
• Make the “Press Enter…” prompt context-aware to respond to Ctrl+C.
• Add entire logout to delete the stored token from the OS keyring (plus basic command registration tests).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
cmd/entire/cli/root.go	Registers the new logout subcommand on the root command.
cmd/entire/cli/logout.go	Implements entire logout by deleting the token from the keyring for the current base URL.
cmd/entire/cli/logout_test.go	Adds tests for logout output/registration/Short description (currently non-hermetic).
cmd/entire/cli/login.go	Splits display vs browser URLs; makes the enter prompt cancellable via context.