update tasklist: phase C complete

TASKLIST.md

@@ -6,13 +6,6 @@
 
 ## Pending
 
-### Phase C -- Architecture
-
-- [ ] Extract `ReconnectManager` to `reconnect.py` (includes `threading.Event`)
-- [ ] Extract `InputHistory` class
-- [ ] Extract `_make_client()` factory (4 duplicate sites)
-- [ ] Cache `_find_root()` result in `ChannelTree.set_state()`
-
 ### Phase D -- Test Coverage
 
 - [ ] Add `ReconnectManager` unit tests
@@ -35,6 +28,13 @@
 
 ## Completed
 
+### Phase C -- Architecture
+
+- [x] Cache `_find_root()` result in `ChannelTree.set_state()`
+- [x] Extract `InputHistory` class
+- [x] Extract `_make_client()` factory (4 duplicate sites)
+- [x] Extract `ReconnectManager` to `reconnect.py` (`threading.Event`)
+
 ### Phase A -- Safety
 
 - [x] Replace `_strip_html` regex with `html.parser` stripper