Close the remaining gaps on Project and Cowork against the wireframes

Re-read both drawings element by element rather than by eye. Five things were
still wrong.

Cowork headed itself "Cowork" — the screen's own name, which the rail already
shows — where the drawing puts the THREAD's title. The title now follows the
conversation, falling back to the screen name for a chat that has none yet;
ChatPanel notifies on load, on reset and when a title is first derived from the
opening turn.

Its files panel read "Tệp đầu ra"; every section heading in the drawings is
caps, so it matches the rail and Monitoring now.

Project kept its three-line explanation above the panes on every visit. The
drawing heads a populated screen with the title alone and gives the text to the
EMPTY state instead, which is where it is actually needed — so it shows only
when there is no project yet.

The workspace path sat as grey caption text where the drawing shows a field. A
read-only line edit looks like one and lets the path be selected and copied.

And Lưu project sat directly under the folder row; the drawing floats it at the
foot of the panel, so a stretch went in above it.

Checked against the control inventory, not just the picture: "Nén" and "Thư mục
Local…" are marked giữ nguyên tại chỗ, so they stay in the status strip even
though the drawing's status line is text only.

New check_cowork_screen; check_project_screen gains the three points. Both
mutation-tested — pinning the title back to tr("cowork.title") and making the
hint unconditional each fail.

23/23 checkers pass. The Qt teardown segfault is still around: check_no_hscroll
took it 1 run in 3, after printing its verdict.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/cowork_tab.py

@@ -81,8 +81,21 @@ class CoworkTab(ChatPanel):
         # succeeds (see _cleanup_turn) — never intermediate files or a folder name.
         on_language_changed(self._retranslate)
 
+    def refresh_title(self) -> None:
+        """Head the screen with the thread you are in, as the drawing does.
+
+        It said "Cowork" on every conversation — the screen's own name, which
+        the rail already shows. The thread's title is the thing that changes and
+        the thing that tells you where you are; a thread with no title yet (a
+        new chat, before its first turn) falls back to the screen name.
+        """
+        lbl = getattr(self, "_title_lbl", None)
+        if lbl is None:
+            return          # ChatPanel.__init__ sets self.title before we exist
+        lbl.setText(getattr(self, "title", "") or tr("cowork.title"))
+
     def _retranslate(self) -> None:
-        self._title_lbl.setText(tr("cowork.title"))
+        self.refresh_title()
         self.skills_btn.setText(tr("cowork.skills_btn"))
         self.skills_btn.setToolTip(tr("cowork.skills_tooltip"))
         self._new_btn.setText(tr("cowork.new_chat"))