git: Detect SCP remotes with non-standard SSH usernames (#59457)

# Objective

The scp-style remote rewrite only treats a leading `user@` as SSH when
the username matches `^[0-9a-zA-Z\-_]+@`. Remotes like
`first.last@host:owner/repo.git` (common on self-hosted instances that
authenticate as the developer) therefore fail to parse, so no hosting
provider matches and Copy Permalink, git blame links, and Open in
browser silently break. Extends #21508, which added `org-000000@`.

## Solution

Match the scp username by exclusion (`^[^/@:]+@`): anything before the
`@` that isn't the `:`/`/` delimiting host and path, mirroring git's scp
syntax. The pattern stays anchored, so `scheme://user@host` URLs aren't
misclassified, and it's a strict superset of the old one, so existing
remotes are unaffected.

## Testing

`cargo test -p git` passes, including two new
`test_parsing_valid_remote_urls` cases — a dotted-username scp remote
(the fix) and a `https://user@host` regression guard. `cargo fmt` and
`cargo clippy -p git` are clean.

## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

---

Release Notes:

- Fixed detection of SSH git remotes whose username contains characters
such as `.` (e.g. `first.last@host:owner/repo.git`), which previously
broke permalinks, git blame links, and "open in browser".

---------

Co-authored-by: dino <dinojoaocosta@gmail.com>

crates/git/src/remote.rs

@@ -9,8 +9,12 @@ use url::Url;
 #[derive(Debug, PartialEq, Eq, Clone, Deref)]
 pub struct RemoteUrl(Url);
 
+// Detect the `user@` prefix of an SCP-like remote (e.g. `git@host:path`). The
+// username may contain anything but the `@`/`:`/`/` that delimit the user,
+// host, and path, so match by exclusion rather than an allowlist that misses
+// names like `first.last`.
 static USERNAME_REGEX: LazyLock<Regex> =
-    LazyLock::new(|| Regex::new(r"^[0-9a-zA-Z\-_]+@").expect("Failed to create USERNAME_REGEX"));
+    LazyLock::new(|| Regex::new(r"^[^/@:]+@").expect("Failed to create USERNAME_REGEX"));
 
 impl FromStr for RemoteUrl {
     type Err = url::ParseError;
@@ -41,6 +45,12 @@ mod tests {
                 "github.com",
                 "/octocat/zed.git",
             ),
+            (
+                "https://jlannister@github.com/octocat/zed.git",
+                "https",
+                "github.com",
+                "/octocat/zed.git",
+            ),
             (
                 "git@github.com:octocat/zed.git",
                 "ssh",
@@ -53,6 +63,12 @@ mod tests {
                 "github.com",
                 "/octocat/zed.git",
             ),
+            (
+                "first.last@gitlab.example.com:group/repo.git",
+                "ssh",
+                "gitlab.example.com",
+                "/group/repo.git",
+            ),
             (
                 "ssh://git@github.com/octocat/zed.git",
                 "ssh",