Add --allow-fallback option to the map command that controls shifted
and ascii (alternate_key) fallback for individual key mappings.
For non-Latin keyboard layouts, when the current layout key is
non-ascii (codepoint > 127 and < 0xE000), the alternate_key from
the base layout is used for matching if the mapping opts in via
--allow-fallback=shifted,ascii.
Default kitty bindings use --allow-fallback=shifted,ascii so they
work out of the box with non-Latin layouts. User custom mappings
default to --allow-fallback=shifted (preserving existing shifted_key
behavior without ascii fallback).
--allow-fallback=none disables all fallback for a mapping.
Python side: parse_options_for_map() in options/utils.py handles flag
parsing, ShortcutMapping uses it in __init__. get_shortcut() filters
candidates by per-mapping allow_fallback.
Go side: ParseMap() handles --allow-fallback, KeyAction stores
AllowFallback, ShortcutTracker.Match passes it to matching.
MatchesParsedShortcut defaults to shifted,ascii for hardcoded shortcuts.
Migrated kittens (themes, command_palette, diff, choose_files) to
use ShortcutTracker with configurable map entries.
Tests added for Python (5 test methods) and Go (ParseMap + key matching).
Follow PEP 0394 and use /usr/bin/env python so that the python in the
users venv is respected. Not that the kitty python files are meant to be
executed standalone anyway, but, whatever.
Fixes#6810
Broke after keyboard refactoring for new keyboard protocol. Now a key
event will match a shortcut specification if either the mods and key
match or mods without shift and shifted key match. Fixes#3314
b3b830bb5f did not actually make `update_encoding()` filter `GLFW_KEY_LAST_PRINTABLE` because `name` contained the key name after applying `symbolic_name()`, which replaces underscores with spaces. Instead of replacing the underscore in `LAST_PRINTABLE` with a space, I moved the check above the call to `symbolic_name()`. This is more readable and future-proof in my opinion.
When adding keys after `GLFW_KEY_UNDERSCORE`, one now needs to change a `#define` right below the last printable key instead of changing it elsewhere in the code.
This commit now also marks `GLFW_KEY_PLUS` and `GLFW_KEY_UNDERSCORE` as printable characters.
