A formula calling a built-in function with too few or too many
arguments (=DATEDIF(a,b), =SUM(), =DATE(2024,1)) was stored and showed
#VALUE! with no hint about what was wrong. Entry now refuses it with
the function's signature, e.g. "DATEDIF has too few arguments. Use
DATEDIF(start_date, end_date, unit)", and leaves the cell unchanged.
Only registered functions are checked: special forms the evaluator
handles itself (IF, LET, LAMBDA...), LAMBDA names and unknown functions
are skipped. Paste and Find & Replace keep turning input that fails
entry into text. DATEDIF's description now lists its units.
Fixes#363
Claude-Session: https://claude.ai/code/session_01BGBBGBC2gRpQ7GDuwQ6WPt
Shirish Veerabattini