[dajiaohuang]

Summary

• Guard copy and single-entry selection actions when the pane has no entries or its cursor is outside the entry range.
• Show a warning instead of dereferencing an empty/null entry array.

Validation

• Task-local C harness generated from the actual changed function bodies reproduced the empty-pane crash before the fix and passed empty-pane and valid-entry cases after it.
• Harness compiled/ran in C99 with Zig 0.14.1; warning-clean with -Wall -Wextra -Werror -Wno-unused-parameter.
• git diff --check passed.
• Full Unix app/UI build not run: no cc or make available; no real filesystem or user directory was used.