fix: systematic byte fidelity for config strings and RV7 gaps

Resolves the 9 gap groups in docs/rewrite/notes/review-rv7-codex.md and
audits every string-typed config field against its consumers
(field -> consumers -> decode status table in final-Z9.md):
- Windows EnvMap keys use a port of Zig's nls.zig uppercase table
  (upcaseW); Windows locale init follows Zig's chain (setlocale +
  _putenv_s); malformed WTF-8 now fails process launch conversions like
  Zig instead of substituting U+FFFD; kitty file paths convert WTF-8.
- bash --rcfile/--init-file, configured TERM and inherited GTK LANG
  keep their original bytes.
- C API clipboard completion and ghostty_surface_binding_action take
  bytes; complete_clipboard_request is byte-typed through the core.
- text:/csi:/esc: bindings, enquiry-response, input = path:, embedded
  initial_input, search needles, titles, link regexes, clipboard
  codepoint map, command palette text and GTK font/namespace values
  decode the escape encoding before use.

Remaining by design: D-Bus a{ss} values and +new-window arguments are
UTF-8 by D-Bus type. C API key/preedit text follows separately.

Test Plan:
- cargo test --workspace
- just check-macos (both), just check-windows, just check-wasm

crates/ghostty-core/src/surface/mod.rs

@@ -459,7 +459,10 @@ impl Surface {
             // don't leak GHOSTTY_LOG to any subprocesses
             env.remove("GHOSTTY_LOG");
 
-            let mut ecfg = exec::Config::new(env, config.term.clone());
+            let mut ecfg = exec::Config::new(
+                env,
+                ghostty_os::osbytes::EncodedOs::from_encoded(config.term.clone()),
+            );
             ecfg.command = command.clone();
             ecfg.env_override = config.env.clone();
             ecfg.shell_integration = config.shell_integration;
@@ -604,7 +607,7 @@ impl Surface {
             rt_app.perform_action(
                 Target::Surface(id),
                 RtAction::SetTitle(SetTitle {
-                    title: title.clone(),
+                    title: ghostty_os::osbytes::config_str_to_text(title),
                 }),
             );
         } else if config.xdg_terminal_exec
@@ -617,7 +620,7 @@ impl Surface {
             rt_app.perform_action(
                 Target::Surface(id),
                 RtAction::SetTitle(SetTitle {
-                    title: cmd.string(),
+                    title: ghostty_os::osbytes::config_str_to_text(&cmd.string()),
                 }),
             );
         } else if let Some(cmd) = &command {
@@ -633,7 +636,7 @@ impl Surface {
                 rt_app.perform_action(
                     Target::Surface(id),
                     RtAction::SetTitle(SetTitle {
-                        title: first.clone(),
+                        title: ghostty_os::osbytes::config_str_to_text(first),
                     }),
                 );
             }
@@ -1303,7 +1306,7 @@ impl Surface {
         // configured title.
         if let Some(title) = &config.title {
             self.perform(RtAction::SetTitle(SetTitle {
-                title: title.clone(),
+                title: ghostty_os::osbytes::config_str_to_text(title),
             }));
         }
 
@@ -2062,7 +2065,7 @@ impl CoreSurface for Surface {
     fn complete_clipboard_request(
         &self,
         req: ClipboardRequest,
-        data: &str,
+        data: &[u8],
         confirmed: bool,
     ) -> Result<(), ClipboardError> {
         Surface::complete_clipboard_request(self, req, data, confirmed)