mcp(fix[pane_tools]): Use tmux-level reset instead of sending keystrokes

why: `clear_pane` called `pane.clear()` which sends the literal text
"reset" + Enter as keystrokes to the pane's foreground process. For
non-shell panes (vim, REPL, TUI), this injects unexpected input. The
tool's contract says "clear the pane" but the annotation says
`destructiveHint: False`, compounding the mismatch.
what:
- Use `pane.reset()` which does tmux-level `send-keys -R \; clear-history`
- This resets the terminal state and clears history without injecting keystrokes

Author: tony

src/libtmux/mcp/tools/pane_tools.py

@@ -314,7 +314,7 @@ def clear_pane(
         session_name=session_name,
         window_id=window_id,
     )
-    pane.clear()
+    pane.reset()
     return f"Pane cleared: {pane.pane_id}"