#handleOAuthFlow now installs an editor.onEscape hook that aborts its
AbortController, and accepts an external abortSignal so the add-wizard
can thread its own controller through (the wizard owns focus and absorbs
Esc itself). Cancellation surfaces as MCPOAuthCancelledError, which the
reauth and add catches translate into a neutral status line instead of
the generic OAuth failure banner. Disambiguated from the existing 5-min
timeout via a userCancelled flag so timeouts still read as errors.
The wizard intercepts Esc/Ctrl+C while #oauthAbort is set so its own
"Press Esc to cancel" advertisement now matches the behaviour, and
renames its error heading + tip when the failure is a user cancel. Also
fixed the misleading "(Press Ctrl+C to cancel)" message in the chat
transcript onAuth block to say "Press Esc" — Ctrl+C is bound to the
editor clear action, not interrupt.
Fixes#3888