fix(input): match Shift+letter bindings when terminal omits SHIFT modifier

[sinelaw]

Summary

Fixes #1899.

Without kitty keyboard protocol, terminals typically encode Shift+letter by sending the uppercase character alone — no SHIFT modifier accompanies it. The previous normalize_key lowercased the char but kept the empty modifier set, so a binding stored as (Char('p'), SHIFT) never matched the incoming (Char('P'), NONE) event.

As reported in #1899, this made Shift+letter shortcuts only fire while Caps Lock was on (which causes some terminals to invert the case and re-introduce the SHIFT modifier on lowercase letters). The same root cause meant the keybinding editor's add-binding dialog captured Shift+P as plain p, losing the shift information at save time.

Approach

• normalize_key now infers SHIFT when an uppercase letter arrives with no other modifiers. The CapsLock+Ctrl+letter → Ctrl+letter collapse is preserved (uppercase + CONTROL is intentionally not given a SHIFT because that case is ambiguous between caps lock and a real shift, and the existing behavior is to fold caps lock away).
• The add-binding dialog (view/keybinding_editor.rs) and the record-key search (app/keybinding_editor/editor.rs) route the recorded event through normalize_key so they capture Shift+P consistently — no matter whether the terminal reported SHIFT.
• The fallback to InsertChar is unaffected: it uses the original event, so typing capital Z in a buffer still inserts Z.

Tests

• test_shift_letter_binding_works_without_terminal_shift_modifier — the core regression: Char('P') with no modifier now matches a Shift+P binding.
• test_capslock_ctrl_letter_still_matches_ctrl_letter_binding — guards the existing CapsLock+Ctrl+A → Ctrl+A behavior.
• test_uppercase_without_binding_falls_through_to_insert_char — confirms typing capital letters still inserts them when no binding exists.
• record_search_key_normalizes_uppercase_letter_to_shift — the record-key search captures the SHIFT modifier even when the terminal omits it.
• add_dialog_records_shift_when_terminal_omits_shift_modifier / add_dialog_records_shift_when_terminal_includes_shift_modifier / add_dialog_preserves_ctrl_when_capturing_upper_letter — full end-to-end dialog drive: send the simulated event through handle_keybinding_editor_input and assert the captured (key_code, modifiers).

Full lib test suite: 2468 passed, 0 failed.

Manual validation

Reproduced and verified the fix end-to-end:

1. Added a Shift+P → save binding in ~/.config/fresh/config.json.
2. Opened a modified buffer (Xinitial content) in fresh under tmux.
3. Pressed P. The status bar transitioned to Saved, the unsaved-changes marker [+] and the buffer's * cleared, and the file on disk reflects the new content.

Test plan

• cargo test -p fresh-editor --lib
• cargo check --all-targets
• cargo check --all-targets --features gui
• cargo fmt --check
• Manual smoke test: Shift+P triggers save via custom binding.

https://claude.ai/code/session_01H6FpwGdLrCA7zquAbVrhX9

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Generated by Claude Code

[sinelaw]

In my terminal (xfce terminal) when enabling caps lock the editor receives only modifier "shift", i.e. "shift"+"A"