fix(deps): pin a patched alacritty to survive deep keyboard-mode pushes

Enabling `kitty_keyboard` (#184) made an upstream `alacritty_terminal` bug
reachable from any foreground program. `push_keyboard_mode` caps its stack by
removing from `title_stack` instead of `keyboard_mode_stack` -- a copy-paste
slip from `push_title` that compiles because both are `Vec`s and the removed
value only feeds a `trace!`.

Two consequences. Each overflowing push silently drops a saved window title, so
a later XTPOPTITLE restores the wrong one. And once the title stack is empty,
`Vec::remove(0)` panics: 4097 unpopped `CSI > 1 u` pushes -- roughly 20KB of
output -- kill the `tty7-remote-reader` thread and freeze the pane. The depth
cap never trimmed `keyboard_mode_stack` at all, so it was doing nothing.

Hostile output is not required. A TUI that pushes without popping (per redraw,
per keypress) reaches 4096 on its own in a long session.

Pin our fork of Zed's fork instead: `tty7` is Zed's `fcf32fe` plus the one-word
fix. No `[patch]` section is needed -- tty7 is the only crate in the tree that
depends on `alacritty_terminal`, so a plain URL/rev swap cannot split it into
two incompatible copies the way the gpui pin would.

The regression test guards the pin rather than our own code: it pushes past the
4096 cap and then queries, using the reply as a liveness probe. Verified to fail
against the unpatched rev.

Still present on alacritty master as of 852e971. Drop the fork once it lands
upstream.

Cargo.lock

@@ -196,7 +196,7 @@ dependencies = [
 [[package]]
 name = "alacritty_terminal"
 version = "0.26.1-dev"
-source = "git+https://github.com/zed-industries/alacritty?rev=fcf32feacb367b75ec84dd40f041e4fd411d3cc1#fcf32feacb367b75ec84dd40f041e4fd411d3cc1"
+source = "git+https://github.com/l0ng-ai/alacritty?rev=22b1d74842732f6ea30d8f4eec768b3ac659d0b6#22b1d74842732f6ea30d8f4eec768b3ac659d0b6"
 dependencies = [
  "base64",
  "bitflags 2.13.0",

Cargo.toml

@@ -65,10 +65,19 @@ image = "0.25"
 # to gpui's rev so the shared `http_client`/`zed-reqwest` versions stay aligned.
 reqwest_client = { git = "https://github.com/zed-industries/zed", rev = "1d217ee39d381ac101b7cf49d3d22451ac1093fe" }
 
-# Zed's fork of alacritty_terminal — same rev Zed pins. Used by the *client*
+# Our fork of Zed's alacritty_terminal fork. Used by the *client*
 # (`terminal::remote`) for the VT parser + grid (`Term`/`ansi::Processor`) that
 # renders the mirror. The daemon's PTY itself is driven by `portable-pty` below.
-alacritty_terminal = { git = "https://github.com/zed-industries/alacritty", rev = "fcf32feacb367b75ec84dd40f041e4fd411d3cc1" }
+#
+# The `tty7` branch is Zed's `fcf32fe` (the rev Zed pins) plus one commit:
+# `push_keyboard_mode` capped its stack by removing from `title_stack` instead of
+# `keyboard_mode_stack` — a copy-paste slip from `push_title` that compiles because
+# both are `Vec`s. With `kitty_keyboard` on (see `terminal_config_from_user`) every
+# overflowing push silently drops a saved title, and once the title stack is empty
+# `Vec::remove(0)` panics — 4097 unpopped `CSI > 1 u` pushes, about 20KB of output,
+# kill the reader thread and freeze the pane. Still present on alacritty master as
+# of 852e971; drop this fork once it lands upstream.
+alacritty_terminal = { git = "https://github.com/l0ng-ai/alacritty", rev = "22b1d74842732f6ea30d8f4eec768b3ac659d0b6" }
 
 # Desktop notifications driven by OSC 9 / OSC 777 escape sequences. Cross-platform;
 # the macOS backend uses the deprecated NSUserNotification (weak — a completion

src/terminal/remote.rs

@@ -1692,6 +1692,46 @@ mod tests {
         );
     }
 
+    /// Guards the `alacritty_terminal` pin, not our own code. Upstream's
+    /// `push_keyboard_mode` trims its stack by removing from `title_stack` — a
+    /// copy-paste slip from `push_title` — so once the title stack is empty the
+    /// `Vec::remove(0)` panics and takes the reader thread with it. Enabling
+    /// `kitty_keyboard` made that reachable from any foreground program: ~20KB of
+    /// unpopped pushes is enough. Our fork fixes it; a bump back to an unpatched
+    /// rev must fail here rather than in the field.
+    #[test]
+    fn deep_keyboard_mode_pushes_leave_the_reader_alive() {
+        let (client_side, mut daemon_side) = UnixStream::pair().unwrap();
+        let term = RemoteTerminal::from_stream(client_side, TermSize::new(80, 24)).unwrap();
+
+        // One past alacritty's KEYBOARD_MODE_STACK_MAX_DEPTH (4096): the push that
+        // overflows is the one that used to panic. The trailing query is the
+        // liveness probe — a dead reader thread simply never answers.
+        let mut payload = b"\x1b[>1u".repeat(4097);
+        payload.extend_from_slice(b"\x1b[?u");
+        DaemonMsg::Output(payload).encode(&mut daemon_side).unwrap();
+        daemon_side.flush().unwrap();
+
+        let mut reply = None;
+        for _ in 0..200 {
+            while let Ok(event) = term.events.try_recv() {
+                if let AlacEvent::PtyWrite(text) = event {
+                    reply = Some(text);
+                }
+            }
+            if reply.is_some() {
+                break;
+            }
+            std::thread::sleep(std::time::Duration::from_millis(5));
+        }
+
+        assert_eq!(
+            reply.as_deref(),
+            Some("\x1b[?1u"),
+            "the reader thread must survive a deep mode-push run and still answer queries"
+        );
+    }
+
     #[test]
     fn spawn_retry_only_for_daemon_disconnects() {
         let eof: anyhow::Error =