feat(keybind): complete emacs keybinding coverage

[wowi42]

The emacs keybind namespace covers basic movement and editing, but many standard GNU Emacs defaults are missing.

Wrong binding

Key	Emacs expects	Current
C-r	isearch-backward	find_file

Missing bindings (command exists)

Key	Emacs command	Flow command
C-l	recenter-top-bottom	scroll_view_center_cycle
M-w	kill-ring-save	copy
M-;	comment-dwim	toggle_comment
M-^	delete-indentation	join_next_line
M-{	backward-paragraph	move_par_begin
M-}	forward-paragraph	move_par_end
M-h	mark-paragraph	select_par
M-g M-g	goto-line	goto_line
C-x C-w	write-file	save_file_as
C-x u	undo	undo
C-x 0	delete-window	close_split
C-x 1	delete-other-windows	-
C-x 2	split-window-below	add_split
C-x 3	split-window-right	add_split
C-x o	other-window	focus_split
C-x left	previous-buffer	previous_tab
C-x right	next-buffer	next_tab
C-x C-x	exchange-point-and-mark	selections_reverse
C-x C-u	upcase-region	to_upper
C-x C-l	downcase-region	to_lower

Missing commands (need implementation)

Key	Emacs command	Description
C-t	transpose-chars	Swap characters at point
M-t	transpose-words	Swap words at point
C-x C-t	transpose-lines	Swap lines
M-u	upcase-word	Uppercase word at point
M-l	downcase-word	Lowercase word at point
M-c	capitalize-word	Capitalize word at point
M-y	yank-pop	Cycle kill-ring
M-%	query-replace	Interactive replace
C-o	open-line	Insert newline without moving cursor
M-z	zap-to-char	Delete up to char
M-\\	delete-horizontal-space	Remove spaces/tabs around point
M-SPC	just-one-space	Collapse whitespace to one space
C-M-f	forward-sexp	Forward over balanced expression
C-M-b	backward-sexp	Backward over balanced expression
C-M-k	kill-sexp	Delete balanced expression
C-M-a	beginning-of-defun	Start of current function
C-M-e	end-of-defun	End of current function

Questions

• Which of the missing commands would be worth implementing? The transpose-* and sexp family likely need tree-sitter or similar support, but upcase-word, downcase-word, capitalize-word, open-line, yank-pop, and query-replace seem straightforward.
• Should the wrong C-r binding and the "command exists" group be fixed first as low-hanging fruit?