fix(tools): Use ANNOTATIONS_CREATE for enter_copy_mode

why: ANNOTATIONS_MUTATING advertises idempotentHint=True, but
enter_copy_mode accepts a scroll_up parameter that, when set to an
integer, accumulates scroll across invocations — calling
enter_copy_mode(scroll_up=50) twice scrolls 100 lines, not 50.
That path is non-idempotent, so the hint should reflect the upper
bound of behavior. ANNOTATIONS_CREATE (idempotentHint=False) is
the safer and more accurate classification, matching send_keys,
paste_text, pipe_pane, and swap_pane — all of which are
non-idempotent in their primary use cases.

exit_copy_mode remains ANNOTATIONS_MUTATING: exiting copy mode
while already out of it is a tmux no-op, so repeated invocations
converge on the same state.

what:
- Switch enter_copy_mode registration from ANNOTATIONS_MUTATING to
  ANNOTATIONS_CREATE in pane_tools.register(). Tag remains
  TAG_MUTATING.

Author: tony

src/libtmux_mcp/tools/pane_tools.py

@@ -1285,7 +1285,7 @@ def register(mcp: FastMCP) -> None:
     )
     mcp.tool(
         title="Enter Copy Mode",
-        annotations=ANNOTATIONS_MUTATING,
+        annotations=ANNOTATIONS_CREATE,
         tags={TAG_MUTATING},
     )(enter_copy_mode)
     mcp.tool(