Fix NoMatches crash: buffer writes until OperationLog is mounted

The worker starts streaming output before the modal screen finishes
composing. Buffer writes until on_mount fires, then flush.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tui/widgets/operation_log.py

@@ -1,3 +1,5 @@
+import asyncio
+
 from rich.text import Text
 from textual.app import ComposeResult
 from textual.screen import ModalScreen
@@ -12,6 +14,8 @@ class OperationLog(ModalScreen[None]):
     def __init__(self, title: str = "Operation Output"):
         super().__init__()
         self._title = title
+        self._mounted_event = asyncio.Event()
+        self._buffer: list[str] = []
 
     def compose(self) -> ComposeResult:
         with Vertical(id="op-log"):
@@ -19,15 +23,32 @@ class OperationLog(ModalScreen[None]):
             yield RichLog(id="ol-log", wrap=True, highlight=True, markup=True)
             yield Button("Close", variant="primary", id="ol-close")
 
+    def on_mount(self) -> None:
+        # Flush any buffered writes
+        log = self.query_one("#ol-log", RichLog)
+        for text in self._buffer:
+            self._write_to_log(log, text)
+        self._buffer.clear()
+        self._mounted_event.set()
+
     def on_button_pressed(self, event: Button.Pressed) -> None:
         self.dismiss(None)
 
     def action_close(self) -> None:
         self.dismiss(None)
 
-    def write(self, text: str) -> None:
-        log = self.query_one("#ol-log", RichLog)
+    def _write_to_log(self, log: RichLog, text: str) -> None:
         if "[" in text and "[/" in text:
             log.write(Text.from_markup(text))
         else:
             log.write(text)
+
+    def write(self, text: str) -> None:
+        if not self._mounted_event.is_set():
+            self._buffer.append(text)
+            return
+        try:
+            log = self.query_one("#ol-log", RichLog)
+            self._write_to_log(log, text)
+        except Exception:
+            self._buffer.append(text)