fix: restore caller panic hook when terminal session ends

README.md

@@ -41,6 +41,8 @@ One crate, four modules, no workspace or frontend-specific types in the editing
 
 Frontends drive `EditorSession::handle` or `execute` and inspect `editor()`; there is no mutable editor getter that could independently alter plugin registration. Pasted text uses `Input::Paste(String)` through the same input seam as keys. Plugin effects are applied internally so a rejected result also retires its owner; there is no generic frontend effects entry point.
 
+The terminal adapter owns raw mode, alternate-screen state, bracketed paste, and its panic hook for one session lifetime. Entry failure, normal return, I/O errors, and unwinding panics restore the caller's hook; active-terminal cleanup runs before caller panic diagnostics. Panics retain their original payload and propagate rather than being swallowed. Terminal state and panic hooks are process-global: run one TUI at a time and do not replace its hook while that session is active.
+
 Built-in Ex commands register as the protected `core` feature in the same command registry used by plugins. External plugins cannot claim core status, replace existing commands, disable core, or bind over essential modal editing keys. `:plugins` lists active features and frontend capabilities.
 
 A feature declares all capabilities it needs. Registration is atomic: if any requirement is unavailable or any command conflicts, none of its commands are installed. For example, `Vamp.plugin "canvas", requires: ["graphics"]` will be refused by this TUI. Capability names are extensible strings, not a terminal-vs-GUI switch. Capability declarations express compatibility; they are not security permissions.
@@ -101,3 +103,5 @@ ruby -c src/ruby_host.rb
 ```
 
 Regression checks exercise Unicode edits, undo/redo, saving and failed saves, capability/command ownership, effect atomicity, real Ruby execution, protocol errors, crash/timeout recovery, and inherited-pipe cleanup. Backend paste checks cover ignored modes, literal Unicode/newline insertion, rejection atomicity, and typing/paste/typing undo and redo. Session checks join real Ruby execution to capability/collision rejection, complete command/binding retirement after invalid effects or host failure, surviving plugins, core editing/saving, and broken-config fallback. The executable was also exercised in PTY sessions for editing/saving, rejected-effect retirement, plugin crash and hang recovery, modal bracketed paste, rejected-paste feedback, undo/redo, scrolling, resize, and terminal restoration.
+
+Unix terminal-hook checks run in isolated child processes and real PTYs to keep global hooks out of the parallel test runner. They cover entry failure, normal return, I/O error, panic cleanup before caller diagnostics, original panic-payload propagation, and later panics producing no stale terminal-restoration output.