Open "Default App" files in the running Warp channel (#9285)

## Description

Fixes #9189. When the user has multiple Warp channels installed (e.g.
Stable + Preview), LaunchServices may register the Stable build as the
default handler for common file types. The "Open File → Default App"
path then resolves to that sibling channel and hands files to Stable
even when the user is running Preview.

The bug sits at `app/src/util/file/external_editor/mac.rs:336`:
`default_app_to_open_path` returns the LaunchServices default,
`Editor::new_from_identifier` has no `dev.warp.*` variants so the result
is dropped, and we fall through to `ctx.open_file_path(full_path)` which
is `[NSWorkspace openURL:]`. NSWorkspace then routes via the same
default-app it just resolved, so the file lands in the other Warp.

The fix detects this case after the existing editor-resolution path: if
the system default is a Warp bundle other than the running channel's
bundle (`ChannelState::app_id()`), open the file with the running
channel's bundle directly via `/usr/bin/open -b`. Non-Warp defaults (VS
Code, TextEdit, etc.) are unaffected, and when the system default
already matches the running channel the override is skipped.

## Testing

Added 2 unit tests in `app/src/util/file/external_editor/mac.rs` for the
new `is_warp_bundle` helper:

- `dev.warp.{Warp,WarpDev,WarpPreview,WarpOss}` → matches
- `com.microsoft.VSCode`, `com.apple.TextEdit`, `dev.zed.Zed`,
`invalid`, empty → does not match

Both pass under `cargo test -p warp --lib
util::file::external_editor::mac::tests`.

The end-to-end behavior (file actually landing in the running channel)
requires a multi-channel macOS install to verify; I didn't manually
reproduce because the build I have access to is the OSS channel only.
Logic is small enough that a Warp dev with Stable + Preview side-by-side
should be able to confirm in seconds.

## Agent Mode
- [ ] Warp Agent Mode - This PR was created via Warp's AI Agent Mode

## Changelog Entries for Stable

CHANGELOG-BUG-FIX: `Open File → Default App` now opens files in the
running Warp channel instead of routing to a different installed Warp.

---------

Co-authored-by: Aloke Desai <aloke@warp.dev>

Author: Faizanq

app/src/util/file/external_editor/mac.rs

@@ -9,6 +9,7 @@ use cocoa::{
     foundation::{NSAutoreleasePool, NSString},
 };
 use command::r#async::Command;
+use warp_core::{channel::ChannelState, AppId};
 use warpui::{platform::mac::make_nsstring, ApplicationBundleInfo};
 
 use super::*;
@@ -344,10 +345,41 @@ pub fn open_file_path_with_line_and_col(
                 return;
             }
         }
+
+        // NSWorkspace's default-app routing can hand files to a sibling
+        // Warp channel (e.g. Stable handling files while Preview is running).
+        // When the resolved default is a different Warp, open with the
+        // running channel's bundle directly.
+        let bundle_id = unsafe { default_app_to_open_path(full_path) };
+        if let Some(bundle_id) = bundle_id.as_deref() {
+            let current = ChannelState::app_id().to_string();
+            if bundle_id != current
+                && is_warp_bundle(bundle_id)
+                && open_with_bundle(&current, full_path)
+            {
+                return;
+            }
+        }
     }
     ctx.open_file_path(full_path);
 }
 
+fn is_warp_bundle(bundle_id: &str) -> bool {
+    AppId::parse(bundle_id)
+        .map(|id| id.qualifier() == "dev" && id.organization() == "warp")
+        .unwrap_or(false)
+}
+
+fn open_with_bundle(bundle_id: &str, path: &Path) -> bool {
+    // Wait for `open` to exit; a non-zero status needs to bubble up so
+    // the caller's ctx.open_file_path fallback still runs.
+    command::blocking::Command::new("/usr/bin/open")
+        .args(["-b", bundle_id])
+        .arg(path)
+        .status()
+        .is_ok_and(|s| s.success())
+}
+
 // Get the Mac default app for opening the file path.
 //
 // The NSString returned by `-[NSBundle bundleIdentifier]` is autoreleased by
@@ -368,3 +400,7 @@ unsafe fn default_app_to_open_path(file_path: &Path) -> Option<String> {
     pool.drain();
     result
 }
+
+#[cfg(test)]
+#[path = "mac_test.rs"]
+mod tests;

app/src/util/file/external_editor/mac_test.rs

@@ -0,0 +1,18 @@
+use super::is_warp_bundle;
+
+#[test]
+fn is_warp_bundle_recognises_warp_channels() {
+    assert!(is_warp_bundle("dev.warp.Warp"));
+    assert!(is_warp_bundle("dev.warp.WarpDev"));
+    assert!(is_warp_bundle("dev.warp.WarpPreview"));
+    assert!(is_warp_bundle("dev.warp.WarpOss"));
+}
+
+#[test]
+fn is_warp_bundle_rejects_other_apps() {
+    assert!(!is_warp_bundle("com.microsoft.VSCode"));
+    assert!(!is_warp_bundle("com.apple.TextEdit"));
+    assert!(!is_warp_bundle("dev.zed.Zed"));
+    assert!(!is_warp_bundle("invalid"));
+    assert!(!is_warp_bundle(""));
+}