fix: async run_tests to prevent zombie cargo processes blocking gates

run_tests MCP tool now spawns tests in the background and returns
immediately. Agents poll get_test_result to check completion. This
prevents zombie cargo processes from holding the build lock when the
CLI times out the MCP call before tests finish.

Also fixes agent permission mode: acceptEdits replaces invalid
allowFullAutoEdit that was causing agents to crash-loop on spawn.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/http/mcp/mod.rs

@@ -1134,7 +1134,7 @@ fn handle_tools_list(id: Option<Value>) -> JsonRpcResponse {
                 },
                 {
                     "name": "run_tests",
-                    "description": "Run the project's test suite (script/test) and return a structured result with pass/fail, test counts, and truncated output. Runs from the project root by default, or from a specific worktree if worktree_path is provided.",
+                    "description": "Start the project's test suite (script/test) as a background job. Returns immediately with {\"status\": \"started\"}. Poll get_test_result with the same worktree_path to check for completion. If the previous run already finished, returns the result inline.",
                     "inputSchema": {
                         "type": "object",
                         "properties": {
@@ -1146,6 +1146,20 @@ fn handle_tools_list(id: Option<Value>) -> JsonRpcResponse {
                         "required": []
                     }
                 },
+                {
+                    "name": "get_test_result",
+                    "description": "Check on a running test job started by run_tests. Returns {\"status\": \"running\", \"elapsed_secs\": N} if still in progress, or the full test result (passed, exit_code, test counts, output) if finished.",
+                    "inputSchema": {
+                        "type": "object",
+                        "properties": {
+                            "worktree_path": {
+                                "type": "string",
+                                "description": "Optional absolute path to the worktree. Must match the worktree_path used in run_tests."
+                            }
+                        },
+                        "required": []
+                    }
+                },
                 {
                     "name": "git_status",
                     "description": "Return the working tree status of an agent's worktree (staged, unstaged, and untracked files). The worktree_path must be inside .huskies/worktrees/. Push and remote operations are not available.",
@@ -1402,6 +1416,7 @@ async fn handle_tools_call(
         // Shell command execution
         "run_command" => shell_tools::tool_run_command(&args, ctx).await,
         "run_tests" => shell_tools::tool_run_tests(&args, ctx).await,
+        "get_test_result" => shell_tools::tool_get_test_result(&args, ctx).await,
         // Git operations
         "git_status" => git_tools::tool_git_status(&args, ctx).await,
         "git_diff" => git_tools::tool_git_diff(&args, ctx).await,
@@ -1526,6 +1541,7 @@ mod tests {
         assert!(names.contains(&"delete_story"));
         assert!(names.contains(&"run_command"));
         assert!(names.contains(&"run_tests"));
+        assert!(names.contains(&"get_test_result"));
         assert!(names.contains(&"git_status"));
         assert!(names.contains(&"git_diff"));
         assert!(names.contains(&"git_add"));