* fix(terminal): harden node PTY relay and terminal session lifecycle
Pin node relay invokes to the authorized node connection (ROUTE_CHANGED
guard), stop node-side input writes to settled/dead PTYs, finalize
sessions on resize failure like write failure, keep surrogate pairs
intact across scrollback and relay prelude truncation, bound the relay
pre-registration output buffer, and buffer Control UI keystrokes typed
while terminal.open/attach is in flight so slow node-relay opens no
longer drop input. Correct the terminal.data seq doc to its real
contract and pin seq monotonicity, seq-gap bounds, input coercion, and
runner event routing with new tests.
* refactor(terminal): extract startup input buffer and fix CI findings
Move Control UI startup input buffering into terminal-startup-input.ts
(LOC budget), drop a stale session-manager comment, remove a map
spread, and fix test typings for event frames and typed mock access.
