fix(tui): the Shift+Enter hint follows the protocol, not a brand list

`shift_enter_unavailable` kept its own list of brands and missed every
other reason the Kitty keyboard protocol gets skipped: JetBrains, screen,
tmux below 3.3 and tmux with `extended-keys off` all swallow it, yet the
prompt still advertised Shift+Enter there. It now reads
`kitty_skip_reason` directly. Two skips deliver the modifier another way
and stay available: Apple Terminal, where `route_enter` polls
CoreGraphics, and Windows Terminal, where the console key record carries
SHIFT — a bare ConHost, only optimistically refined to Windows Terminal,
keeps advertising Alt+Enter.

The old list also carried a `VTE_VERSION >= 8200` cutoff, citing VTE
0.82.0 as the first release with the protocol. It is not: at tag 0.82.0
the string "kitty" appears nowhere in `src/parser-seq.py`, `src/vte.cc`
or `src/widget.cc`, and `_vte_keymap_GDK_Return` encodes only Alt
(`ESC CR`), so Shift+Enter leaves a VTE terminal as the same bare CR as
Enter. Every VTE now advertises Alt+Enter, and `/terminal-setup` stops
telling GNOME Terminal users to upgrade to a version that would not
help. It also stops advertising Alt+Enter to WezTerm, which binds that
chord to ToggleFullScreen.

crates/codegen/kigi-tui/src/slash/commands/terminal_setup.rs

@@ -96,16 +96,15 @@ impl SlashCommand for TerminalSetupCommand {
 
         // Some terminals can't distinguish Shift+Enter from bare Enter at
         // the byte level because the Kitty keyboard protocol isn't
-        // negotiated (VTE < 0.82, or VS Code's xterm.js which mis-encodes
-        // shifted keys). Point users at Alt+Enter, which is reliably
-        // delivered as ESC+CR. Suppressed when the WezTerm warning fired:
-        // stock WezTerm binds Alt+Enter to ToggleFullScreen, so advertising
-        // it would contradict that warning's `\`+Enter guidance.
-        if ctx.shift_enter_unavailable() && !wezterm_kkp_off {
+        // negotiated (VTE, VS Code's xterm.js, a multiplexer that eats
+        // extended keys). Point users at Alt+Enter, which is reliably
+        // delivered as ESC+CR. Never for WezTerm: it binds Alt+Enter to
+        // ToggleFullScreen, so its own warning's `\`+Enter guidance stands.
+        if ctx.shift_enter_unavailable() && !wezterm_kkp_off && ctx.brand != TerminalName::WezTerm {
             let detail = if ctx.vte_version.is_some() || ctx.brand == TerminalName::Vte {
                 match ctx.vte_version.as_deref() {
-                    Some(v) => format!("VTE {v}; need >= 8200 for Shift+Enter"),
-                    None => "legacy VTE; need VTE >= 0.82 for Shift+Enter".to_owned(),
+                    Some(v) => format!("VTE {v}: no Kitty keyboard protocol"),
+                    None => "VTE: no Kitty keyboard protocol".to_owned(),
                 }
             } else if matches!(
                 ctx.brand,