Git uncommit warning (#25977)

Adds a prompt when clicking the uncommit button when the current commit
is already present on a remote branch:

![screenshot showing
prompt](https://github.com/user-attachments/assets/d6421875-588e-4db0-aee0-a92f36bce94b)

Release Notes:

- N/A

---------

Co-authored-by: Conrad <conrad@zed.dev>

crates/proto/proto/zed.proto

@@ -336,6 +336,9 @@ message Envelope {
         GitGetBranches git_get_branches = 312;
         GitCreateBranch git_create_branch = 313;
         GitChangeBranch git_change_branch = 314; // current max
+
+        CheckForPushedCommits check_for_pushed_commits = 315;
+        CheckForPushedCommitsResponse check_for_pushed_commits_response = 316; // current max
     }
 
     reserved 87 to 88;
@@ -2875,3 +2878,13 @@ message GitChangeBranch {
     uint64 work_directory_id = 3;
     string branch_name = 4;
 }
+
+message CheckForPushedCommits {
+    uint64 project_id = 1;
+    uint64 worktree_id = 2;
+    uint64 work_directory_id = 3;
+}
+
+message CheckForPushedCommitsResponse {
+  repeated string pushed_to = 1;
+}

crates/proto/src/proto.rs

@@ -454,6 +454,8 @@ messages!(
     (RemoteMessageResponse, Background),
     (GitCreateBranch, Background),
     (GitChangeBranch, Background),
+    (CheckForPushedCommits, Background),
+    (CheckForPushedCommitsResponse, Background),
 );
 
 request_messages!(
@@ -598,6 +600,7 @@ request_messages!(
     (Pull, RemoteMessageResponse),
     (GitCreateBranch, Ack),
     (GitChangeBranch, Ack),
+    (CheckForPushedCommits, CheckForPushedCommitsResponse),
 );
 
 entity_messages!(
@@ -701,6 +704,7 @@ entity_messages!(
     Pull,
     GitChangeBranch,
     GitCreateBranch,
+    CheckForPushedCommits,
 );
 
 entity_messages!(