fix: resolve command to full exec path for Windows PATHEXT

Author: daithyy

lua/agentic/acp/acp_transport.lua

@@ -77,6 +77,15 @@ function M.create_stdio_transport(config, callbacks)
     function transport:start()
         callbacks.on_state_change("connecting")
 
+        -- Resolve command to full executable path for Windows OS PATHEXT support
+        -- vim.fn.exepath handles .CMD, .EXE and .BAT extensions on Windows
+        local command = vim.fn.exepath(config.command)
+        if command == "" then
+            -- if exepath returns empty, the command is not found in PATH
+            callbacks.on_state_change("error")
+            error(string.format("Command not found: %s", config.command))
+        end
+
         local stdin = uv.new_pipe(false)
         local stdout = uv.new_pipe(false)
         local stderr = uv.new_pipe(false)
@@ -116,7 +125,7 @@ function M.create_stdio_transport(config, callbacks)
         end
 
         --- @diagnostic disable-next-line: missing-fields
-        local handle, pid = uv.spawn(config.command, {
+        local handle, pid = uv.spawn(command, {
             args = args,
             env = final_env,
             stdio = { stdin, stdout, stderr },