mailbox notify: name the protocol, because docker exec hides the terminal

Auto-detection is useless in the deployment this ships in, measured on tor-ms22.
Terminal identity lives in env vars set by the emulator (KITTY_WINDOW_ID,
TERM_PROGRAM) and docker exec does not forward them — pi inside the container
sees only TERM=xterm-256color no matter what is rendering it. So the =desktop
detection can never see Kitty from in there and always falls through to OSC 777,
which Kitty does not implement. Result: on a containerised client the ping
silently does nothing, which is the worst available failure for a feature whose
entire purpose is to break a silence.

Adds MEMPALACE_MAILBOX_NOTIFY=kitty and =osc777 to force one protocol and skip
detection. =desktop keeps the notify.ts-style autodetect for the non-container
case, unset still means in-TUI only, 0/off still silent. The Windows toast branch
is dropped from the comment rather than the code path it never had here: it needs
powershell.exe on PATH, which is a WSL fact, not a Linux-container one.

extensions/pi/mempalace.ts

@@ -1183,20 +1183,37 @@ export default async function mempalaceExtension(pi: ExtensionAPI) {
 	//                    emulator on the human's machine. Opt-in because writing raw
 	//                    escapes to stdout is a behaviour change on shared machines,
 	//                    not because it is unreliable.
+	//   =kitty =osc777   force one protocol, skipping detection entirely.
 	//   =0               silent, for anyone who wants the mailbox without pings.
 	//
+	// WHY FORCING EXISTS — measured on tor-ms22 2026-08-26, and it invalidates
+	// detection in exactly the deployment this ships in. Terminal identity lives in
+	// env vars set by the emulator (KITTY_WINDOW_ID, TERM_PROGRAM) and `docker exec`
+	// does NOT forward them: inside the container pi sees only TERM=xterm-256color
+	// no matter what is rendering it. So detection can never see Kitty from in here
+	// and always falls through to OSC 777, which Kitty does not implement — on a
+	// containerised client the notification would silently do nothing, the worst
+	// possible failure for a feature whose whole job is to break a silence. Naming
+	// the protocol ends the guessing.
+	//
 	// Fired only when something is actually due, i.e. the same condition as the
 	// delivery itself: a notification that fires on an empty poll would teach its
 	// reader to ignore it, which is the failure this whole feature exists to undo.
 	const mailboxNotifyMode = (process.env.MEMPALACE_MAILBOX_NOTIFY ?? "").trim().toLowerCase();
 	const mailboxNotifyEnabled = mailboxNotifyMode !== "0" && mailboxNotifyMode !== "off";
-	const mailboxNotifyDesktop = mailboxNotifyMode === "desktop";
+	const mailboxNotifyTerminal =
+		mailboxNotifyMode === "desktop" ||
+		mailboxNotifyMode === "kitty" ||
+		mailboxNotifyMode === "osc777";
 
 	/** Terminal-native notification. Best-effort; never throws into a handler. */
 	const notifyTerminal = (title: string, body: string): void => {
 		try {
 			const esc = (s: string): string => s.replace(/[\x00-\x1f\x7f;]/g, " ");
-			if (process.env.KITTY_WINDOW_ID) {
+			if (
+				mailboxNotifyMode === "kitty" ||
+				(mailboxNotifyMode === "desktop" && !!process.env.KITTY_WINDOW_ID)
+			) {
 				process.stdout.write(`\x1b]99;i=1:d=0;${esc(title)}\x1b\\`);
 				process.stdout.write(`\x1b]99;i=1:p=body;${esc(body)}\x1b\\`);
 				return;
@@ -1257,7 +1274,7 @@ export default async function mempalaceExtension(pi: ExtensionAPI) {
 					} catch {
 						/* ignore: UI may be gone by the time the poll resolves */
 					}
-					if (mailboxNotifyDesktop) notifyTerminal("MemPalace mailbox", summary);
+					if (mailboxNotifyTerminal) notifyTerminal("MemPalace mailbox", summary);
 				}
 			} catch {
 				/* best-effort delivery: never break a turn over a mailbox read */