fix(update): never self-update the desktop app's Engine

Add InstallMethod::DesktopApp for an Engine inside a macOS
`*.app/Contents/MacOS/` bundle or the desktop app's pinned
`<CODEWHALE_HOME>/gpui/engine/` store. It does not support self-update,
so `codewhale update`, target validation and `uninstall` refuse to write
there, and the CLI, /update and the TUI notice say to use
Codewhale > Check for Updates instead of printing GitHub migration help.

Verified on a Linux Boat VM against origin/main plus this series (debug build): cargo build -p codewhale-cli and cargo check --workspace --all-targets --locked clean (0 errors, 0 warnings); cargo test -p codewhale-release 57 passed; codewhale-cli update:: 109 passed. Fixture in a temp HOME: `update` from X/Codewhale.app/Contents/MacOS/codewhale prints the desktop message and exits 1, `uninstall` names the app, bundle bytes unchanged. Not exercised: a real signed desktop bundle on macOS.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/cli/src/update.rs

@@ -317,6 +317,9 @@ fn managed_install_warning(method: InstallMethod) -> Option<String> {
     if method.supports_self_update() {
         return None;
     }
+    if method == InstallMethod::DesktopApp {
+        return Some(codewhale_release::install::DESKTOP_APP_UPDATE_HELP.to_string());
+    }
     Some(format!(
         "This executable is managed by {label}; in-place self-update is disabled.\n\n\
          {GITHUB_MIGRATION_HELP}\n\n\

crates/release/src/install.rs

@@ -41,6 +41,10 @@ Keep the chosen PATH directory in your shell profile after verifying it.
 Windows: https://github.com/codewhale-hq/CodeWhale/releases/latest
 PATH and migration: https://github.com/codewhale-hq/CodeWhale/blob/main/docs/INSTALL.md"#;
 
+pub const DESKTOP_APP_UPDATE: &str = "Codewhale > Check for Updates";
+
+pub const DESKTOP_APP_UPDATE_HELP: &str = "The Codewhale app updates this copy together with the app. Use Codewhale > Check for Updates. `codewhale update` never writes inside the app.";
+
 /// The package manager (if any) that owns the running executable.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum InstallMethod {
@@ -56,6 +60,7 @@ pub enum InstallMethod {
     Scoop,
     /// A WinGet portable package under `Microsoft/WinGet/Packages`.
     WinGet,
+    DesktopApp,
     /// A release binary the user placed on disk themselves. The default, and
     /// the only case where in-place self-update is correct.
     Binary,
@@ -130,6 +135,16 @@ impl InstallMethod {
 
         let has = |name: &str| components.iter().any(|c| c == name);
 
+        if components
+            .windows(3)
+            .any(|parts| parts[0].ends_with(".app") && parts[1] == "contents" && parts[2] == "macos")
+            || components
+                .windows(2)
+                .any(|pair| pair[0] == "gpui" && pair[1] == "engine")
+        {
+            return Self::DesktopApp;
+        }
+
         // npm is checked first: a `node_modules` install *inside* a Homebrew
         // or Termux prefix is still npm's to update.
         if has("node_modules") {
@@ -168,6 +183,7 @@ impl InstallMethod {
             "omarchy" => Some(Self::Omarchy),
             "scoop" => Some(Self::Scoop),
             "winget" => Some(Self::WinGet),
+            "desktop" | "app" => Some(Self::DesktopApp),
             "binary" | "release" => Some(Self::Binary),
             _ => None,
         }
@@ -188,6 +204,7 @@ impl InstallMethod {
             Self::Omarchy => "omarchy update",
             Self::Scoop => "scoop update codewhale",
             Self::WinGet => "winget upgrade --id HunterBown.CodeWhale",
+            Self::DesktopApp => DESKTOP_APP_UPDATE,
             Self::Binary => "codewhale update",
         }
     }
@@ -205,6 +222,7 @@ impl InstallMethod {
             }
             Self::Scoop => "scoop uninstall codewhale",
             Self::WinGet => "winget uninstall --id HunterBown.CodeWhale",
+            Self::DesktopApp => "remove the Codewhale app; this Engine is part of it",
             Self::Binary => "codewhale uninstall --yes",
         }
     }
@@ -228,6 +246,7 @@ impl InstallMethod {
             Self::Omarchy => "Omarchy",
             Self::Scoop => "Scoop",
             Self::WinGet => "WinGet",
+            Self::DesktopApp => "the Codewhale app",
             Self::Binary => "release binary",
         }
     }

crates/tui/src/commands/groups/utility/update.rs

@@ -129,6 +129,9 @@ pub(super) fn resolve_updater(
 
 /// Instructions for an install this command must not update in place.
 pub(super) fn managed_install_message(method: InstallMethod) -> String {
+    if method == InstallMethod::DesktopApp {
+        return codewhale_release::install::DESKTOP_APP_UPDATE_HELP.to_string();
+    }
     format!(
         "Codewhale was installed with {label}, which owns this binary.\n\
          {migration_help}\n\n\

crates/tui/src/tui/ui.rs

@@ -1414,6 +1414,13 @@ impl UpdateNotice {
     /// Short line for the transient status toast, naming the command that
     /// actually updates *this* install.
     fn toast_line(&self, install: InstallMethod) -> String {
+        if install == InstallMethod::DesktopApp {
+            return format!(
+                "v{latest} available - use {command}",
+                latest = self.latest,
+                command = install.update_command()
+            );
+        }
         format!(
             "v{latest} available - run `{command}` and restart",
             latest = self.latest,
@@ -1437,7 +1444,9 @@ impl UpdateNotice {
     /// Homebrew or npm owns leaves the manager's metadata lying about what is
     /// on disk, and the next upgrade silently reverts the user.
     fn notice_block(&self, install: InstallMethod) -> String {
-        let action = if install.supports_self_update() {
+        let action = if install == InstallMethod::DesktopApp {
+            codewhale_release::install::DESKTOP_APP_UPDATE_HELP.to_string()
+        } else if install.supports_self_update() {
             "Run `/update install` here (preview it with a bare `/update`), or `codewhale update` in a shell, then restart Codewhale."
                 .to_string()
         } else {