zed: Support IPv6 hosts in SCP-style SSH URLs (#62157)

# Objective

- Support opening remote paths from SCP-style SSH URLs that use
bracketed IPv6 hosts, such as `ssh://[2600::]:~/foo`.

## Solution

- Validate SSH hosts with `url::Host::parse`, which supports bracketed
IPv6 addresses while continuing to reject malformed or ambiguous hosts.
- Add test coverage for IPv6 URLs with usernames, home-relative paths,
absolute paths, and explicit ports.
- Add rejection tests for unbracketed IPv6 addresses and ambiguous
port-plus-SCP-path syntax.

## Testing

- Ran `cargo fmt --all -- --check`.
- Ran `cargo test -p zed test_parse_ssh_urls -- --nocapture`.
- Ran `cargo test -p zed test_reject_ssh_urls -- --nocapture`.
- All targeted tests passed on macOS. No additional platform-specific
testing is expected to be necessary because the change only affects URL
parsing.

Release Notes:

- Fixed opening remote paths from SCP-style SSH URLs with IPv6 hosts.

Signed-off-by: Xiaobo Liu <cppcoffee@gmail.com>

crates/zed/src/zed/open_listener.rs

@@ -329,8 +329,7 @@ fn parse_ssh_url(url: &str) -> Result<url::Url> {
     // They are unsupported by Url::parse, but can be normalized into a Url.
     //   SCPUrl("ssh://user@host:~/relpath") => Url("ssh://user@host/~/relpath")
     //   SCPUrl("ssh://user@host:/abs/path") => Url("ssh://user@host/abs/path")
-    //
-    // TODO: Add IPv6 support: "ssh://[2600::]:~/foo"
+    //   SCPUrl("ssh://[2600::]:~/foo") => Url("ssh://[2600::]/~/foo")
     let ssh_target = url
         .strip_prefix("ssh://")
         .with_context(|| format!("invalid ssh url: {url}"))?;
@@ -347,7 +346,7 @@ fn parse_ssh_url(url: &str) -> Result<url::Url> {
         .rsplit_once('@')
         .map_or((None, authority), |(userinfo, host)| (Some(userinfo), host));
     anyhow::ensure!(
-        !host.is_empty() && !host.starts_with('[') && !host.contains(':'),
+        !host.is_empty() && url::Host::parse(host).is_ok(),
         "invalid ssh url: {url}"
     );
 
@@ -1235,6 +1234,38 @@ mod tests {
                 None,
                 "/project",
             ),
+            (
+                "ssh://[2600::]:~/foo",
+                Some("ssh://[2600::]/~/foo"),
+                "2600::",
+                None,
+                None,
+                "/~/foo",
+            ),
+            (
+                "ssh://me@[2001:db8::1]:~/project",
+                Some("ssh://me@[2001:db8::1]/~/project"),
+                "2001:db8::1",
+                Some("me"),
+                None,
+                "/~/project",
+            ),
+            (
+                "ssh://me@[::1]:/tmp/file",
+                Some("ssh://me@[::1]/tmp/file"),
+                "::1",
+                Some("me"),
+                None,
+                "/tmp/file",
+            ),
+            (
+                "ssh://[2001:db8::2]:2222/tmp",
+                Some("ssh://[2001:db8::2]:2222/tmp"),
+                "2001:db8::2",
+                None,
+                Some(2222),
+                "/tmp",
+            ),
         ];
 
         for (input, expected_url, host, username, port, path) in cases {
@@ -1362,7 +1393,8 @@ mod tests {
         for input in [
             "ssh://me@localhost:code/vibes/mine-bot",
             "ssh://me@localhost:2222:~/project",
-            "ssh://me@[2001:db8::1]:~/project",
+            "ssh://2600:::~/foo",
+            "ssh://[2600::]:2222:~/foo",
         ] {
             let result = cx.update(|cx| {
                 OpenRequest::parse(