Fix terminal resize handling by sending SIGWINCH to asciinema process

Replace approach of signaling pane processes with proper SIGWINCH signal
to the asciinema recording process itself. This correctly triggers "r"
(resize) events in cast files when switching between panes of different
dimensions.

- Send SIGWINCH to asciinema_pid instead of pane process group
- Asciinema detects terminal size changes and records resize events
- Ensures proper playback with correct terminal dimensions
- Fix recordings showing wrong terminal size when switching panes

This resolves issues where pane switching didn't generate resize events
in recordings, causing playback to display with incorrect dimensions.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: bitplane

pyproject.toml

@@ -1,7 +1,7 @@
 [project]
 name = "tvmux"
 description = "terminal multiplexer recorder"
-version = "0.5.0"
+version = "0.5.1"
 authors = [
     { name = "Gareth Davidson", email = "gaz@bitplane.net" }
 ]

src/tvmux/models/recording.py

@@ -121,6 +121,23 @@ def switch_pane(self, new_pane_id: str):
 
         self.active_pane = new_pane_id
 
+        # Send SIGWINCH to the new pane's process group to trigger resize handling
+        self._send_sigwinch(new_pane_id)
+
+    def _send_sigwinch(self, pane_id: str):
+        """Send SIGWINCH signal to asciinema process to handle terminal resize in recording."""
+        if not self.asciinema_pid:
+            logger.warning("No asciinema process to send SIGWINCH to")
+            return
+
+        try:
+            subprocess.run([
+                "kill", "-SIGWINCH", str(self.asciinema_pid)
+            ], check=True)
+            logger.debug(f"Sent SIGWINCH to asciinema process {self.asciinema_pid} for pane {pane_id}")
+        except subprocess.CalledProcessError as e:
+            logger.warning(f"Failed to send SIGWINCH to asciinema process {self.asciinema_pid}: {e}")
+
     def stop(self):
         """Stop recording."""
         if not self.active:
@@ -225,7 +242,7 @@ def _dump_pane(self, pane_id: str):
                 f.write("\033[?7h")      # Enable auto-wrap mode
                 f.write("\033[?25h")     # Show cursor (will be overridden later if needed)
 
-                # Get primary buffer content
+                # 4. Get and send primary buffer content
                 primary_result = subprocess.run([
                     "tmux", "capture-pane", "-t", pane_target, "-e", "-p"
                 ], capture_output=True, text=True)
@@ -234,11 +251,11 @@ def _dump_pane(self, pane_id: str):
                     primary_content = primary_result.stdout.rstrip('\n')
                     f.write(primary_content)
 
-                # 4. If in alternate screen mode, switch to it
+                # 5. If in alternate screen mode, switch to it
                 if alternate_on:
                     f.write("\033[?1049h")  # Enable alternate screen buffer
 
-                    # 5. If alt mode is on, dump the contents of the alt buffer
+                    # 6. If alt mode is on, dump the contents of the alt buffer
                     alt_result = subprocess.run([
                         "tmux", "capture-pane", "-t", pane_target, "-a", "-e", "-p"
                     ], capture_output=True, text=True)
@@ -251,11 +268,11 @@ def _dump_pane(self, pane_id: str):
                         # Use alternate screen cursor position
                         cursor_x, cursor_y = alt_saved_x, alt_saved_y
 
-                # 6. Set up scroll region, cursor visibility, raw mode, etc.
+                # 7. Set up scroll region, cursor visibility, raw mode, etc.
                 # TODO: Get actual scroll region from tmux if available
                 # For now, just handle cursor visibility
 
-                # 7. Reposition the text cursor
+                # 8. Reposition the text cursor
                 config = get_config()
                 if config.annotations.include_cursor_state:
                     row = cursor_y + 1  # Convert to 1-based