feat: add get_version MCP tool returning version and build hash

Agents can now call get_version to see what server version and commit
they're running against.

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

server/src/http/mcp/diagnostics.rs

@@ -319,6 +319,17 @@ pub(super) fn tool_dump_crdt(args: &Value) -> Result<String, String> {
     .map_err(|e| format!("Serialization error: {e}"))
 }
 
+/// MCP tool: return the server version and build hash.
+pub(super) fn tool_get_version() -> Result<String, String> {
+    let build_hash = std::fs::read_to_string(".huskies/build_hash")
+        .unwrap_or_else(|_| "unknown".to_string());
+    serde_json::to_string_pretty(&json!({
+        "version": env!("CARGO_PKG_VERSION"),
+        "build_hash": build_hash.trim(),
+    }))
+    .map_err(|e| format!("Serialization error: {e}"))
+}
+
 /// MCP tool: count lines in a specific file relative to the project root.
 pub(super) fn tool_loc_file(args: &Value, ctx: &AppContext) -> Result<String, String> {
     let file_path = args

server/src/http/mcp/mod.rs

@@ -837,6 +837,14 @@ fn handle_tools_list(id: Option<Value>) -> JsonRpcResponse {
                         }
                     }
                 },
+                {
+                    "name": "get_version",
+                    "description": "Return the server version and build hash.",
+                    "inputSchema": {
+                        "type": "object",
+                        "properties": {}
+                    }
+                },
                 {
                     "name": "rebuild_and_restart",
                     "description": "Rebuild the server binary from source and re-exec with the new binary. Gracefully stops all running agents before restart. If the build fails, the server stays up and returns the build error.",
@@ -1266,6 +1274,7 @@ async fn handle_tools_call(
         "get_pipeline_status" => story_tools::tool_get_pipeline_status(ctx),
         // Diagnostics
         "get_server_logs" => diagnostics::tool_get_server_logs(&args),
+        "get_version" => diagnostics::tool_get_version(),
         // Server lifecycle
         "rebuild_and_restart" => diagnostics::tool_rebuild_and_restart(ctx).await,
         // Permission bridge (Claude Code → frontend dialog)
@@ -1423,7 +1432,8 @@ mod tests {
         assert!(names.contains(&"status"));
         assert!(names.contains(&"loc_file"));
         assert!(names.contains(&"dump_crdt"));
-        assert_eq!(tools.len(), 62);
+        assert!(names.contains(&"get_version"));
+        assert_eq!(tools.len(), 63);
     }
 
     #[test]