fix(git): add SSH channel lifecycle logging and fix password auth username check

- Remove user=="git" restriction from auth_password: the actual user is
  determined by the token, not the SSH username, matching Gitea's approach
- Add channel_open_session logging with explicit flush to verify
  CHANNEL_OPEN_CONFIRMATION reaches the client
- Add pty_request handler (reject with log) so git clients that request
  a PTY are handled gracefully instead of falling through to default
- Add subsystem_request handler (log + accept) so git subsystems are
  visible in logs
- Prefix unused variables with _ to eliminate warnings

libs/git/ssh/handle.rs

@@ -163,19 +163,12 @@ impl russh::server::Handler for SSHandle {
         Ok(Auth::UnsupportedMethod)
     }
 
-    async fn auth_password(&mut self, user: &str, token: &str) -> Result<Auth, Self::Error> {
+    async fn auth_password(&mut self, _user: &str, token: &str) -> Result<Auth, Self::Error> {
         let client_info = self
             .client_addr
             .map(|addr| format!("{}", addr))
             .unwrap_or_else(|| "unknown".to_string());
 
-        if user != "git" {
-            warn!(
-                self.logger,
-                "auth_password rejected: invalid username '{}', client: {}", user, client_info
-            );
-            return Err(russh::Error::NotAuthenticated);
-        }
 
         if token.is_empty() {
             warn!(
@@ -423,11 +416,56 @@ impl russh::server::Handler for SSHandle {
 
     async fn channel_open_session(
         &mut self,
-        _: Channel<Msg>,
-        _: &mut Session,
+        channel: Channel<Msg>,
+        session: &mut Session,
     ) -> Result<bool, Self::Error> {
+        let client_info = self
+            .client_addr
+            .map(|addr| format!("{}", addr))
+            .unwrap_or_else(|| "unknown".to_string());
+        info!(self.logger, "channel_open_session"; "channel" => ?channel, "client" => %client_info);
+        let _ = session.flush().ok();
         Ok(true)
     }
+
+    async fn pty_request(
+        &mut self,
+        channel: ChannelId,
+        term: &str,
+        col_width: u32,
+        row_height: u32,
+        _pix_width: u32,
+        _pix_height: u32,
+        _modes: &[(russh::Pty, u32)],
+        session: &mut Session,
+    ) -> Result<(), Self::Error> {
+        let client_info = self
+            .client_addr
+            .map(|addr| format!("{}", addr))
+            .unwrap_or_else(|| "unknown".to_string());
+        warn!(self.logger, "pty_request (not supported)";
+            "channel" => ?channel, "term" => %term, "cols" => col_width, "rows" => row_height, "client" => %client_info);
+        let _ = session.flush().ok();
+        Ok(())
+    }
+
+    async fn subsystem_request(
+        &mut self,
+        channel: ChannelId,
+        name: &str,
+        session: &mut Session,
+    ) -> Result<(), Self::Error> {
+        let client_info = self
+            .client_addr
+            .map(|addr| format!("{}", addr))
+            .unwrap_or_else(|| "unknown".to_string());
+        info!(self.logger, "subsystem_request";
+            "channel" => ?channel, "subsystem" => %name, "client" => %client_info);
+        // git-clients may send "subsystem" for git protocol over ssh.
+        // We don't use subsystem; exec_request handles it directly.
+        let _ = session.flush().ok();
+        Ok(())
+    }
     async fn data(
         &mut self,
         channel: ChannelId,