fix(tui): add legacy terminal support for shift+letter shortcuts

In legacy terminals, Shift+P produces uppercase 'P' instead of
Kitty protocol sequences. Add fallback to check uppercase letters
for shift+letter combinations.

packages/tui/src/keys.ts

@@ -418,6 +418,12 @@ export function matchesKey(data: string, keyId: KeyId): boolean {
 			return matchesKittySequence(data, codepoint, MODIFIERS.shift + MODIFIERS.ctrl);
 		}
 
+		if (shift && !ctrl && !alt) {
+			// Legacy: shift+letter produces uppercase
+			if (data === key.toUpperCase()) return true;
+			return matchesKittySequence(data, codepoint, MODIFIERS.shift);
+		}
+
 		if (modifier !== 0) {
 			return matchesKittySequence(data, codepoint, modifier);
 		}