fix: await send_message chain to eliminate flaky user_message_count test (#368)

send_message fired off the .and_then/.catch chain without awaiting it,
causing the user_message_count decrement to be deferred via
vim.schedule_wrap. The test relied on vim.wait(50ms) polling which was
insufficient on macOS CI runners.

Await the chain inside send_message (already Promise.async) so the
promise reflects the full operation lifecycle, and replace the polling
loops in tests with deterministic :wait() calls.

Author: jbro

lua/opencode/services/messaging.lua

@@ -83,6 +83,7 @@ M.send_message = Promise.async(function(prompt, opts)
       update_sent_message_count(-1)
       session_runtime.cancel():await()
     end)
+    :await()
 end)
 
 ---@param prompt string

tests/unit/services_messaging_spec.lua

@@ -78,7 +78,6 @@ describe('opencode.services.messaging', function()
 
     local count_before = state.user_message_count['sess1'] or 0
     local count_during = nil
-    local count_after = nil
 
     local orig = state.api_client.create_message
     state.api_client.create_message = function(_, sid, params)
@@ -90,12 +89,9 @@ describe('opencode.services.messaging', function()
       })
     end
 
-    messaging.send_message('hello world')
+    messaging.send_message('hello world'):wait()
 
-    vim.wait(50, function()
-      count_after = state.user_message_count['sess1'] or 0
-      return count_after == 0
-    end)
+    local count_after = state.user_message_count['sess1'] or 0
 
     assert.equal(0, count_before)
     assert.equal(1, count_during)
@@ -111,7 +107,6 @@ describe('opencode.services.messaging', function()
 
     local count_before = state.user_message_count['sess1'] or 0
     local count_during = nil
-    local count_after = nil
 
     local orig = state.api_client.create_message
     state.api_client.create_message = function(_, sid, params)
@@ -120,14 +115,11 @@ describe('opencode.services.messaging', function()
     end
 
     local orig_cancel = session_runtime.cancel
-    stub(session_runtime, 'cancel')
+    stub(session_runtime, 'cancel').returns(Promise.new():resolve(nil))
 
-    messaging.send_message('hello world')
+    messaging.send_message('hello world'):wait()
 
-    vim.wait(50, function()
-      count_after = state.user_message_count['sess1'] or 0
-      return count_after == 0
-    end)
+    local count_after = state.user_message_count['sess1'] or 0
 
     assert.equal(0, count_before)
     assert.equal(1, count_during)