fix: close remaining gaps found by the completeness audit

Addresses the partial ports listed in
docs/rewrite/notes/review-completeness-codex.md (details in
docs/rewrite/notes/gaps-X2.md):
- Flatpak: the exit watcher no longer consumes the host command; a
  shared FlatpakSignalHandle lets closing a surface still SIGHUP the
  host process group.
- Child environment is byte-preserving end to end (ghostty_os::EnvMap
  of OsStrings) and Snap paths are filtered like filterSnapPaths.
- argv handling no longer panics on non-UTF-8 arguments.
- URI percent-decoding keeps raw bytes; OSC 7 pwd is passed through
  without lossy conversion.
- Keybinding comparison/hashing uses full Unicode case folding from a
  table generated from CaseFolding.txt (Unicode 17.0.0).
- Link regexes set Oniguruma's whole-search retry limit through the new
  minimal ghostty-onig crate (one SAFETY-commented FFI call).
- OSC 9 NUL-capacity check ordering matches Zig.
- Wayland registry binds/clears globals advertised after startup.
- Custom shaders may pass sampler2D to helper functions (naga adapter).
- +list-themes preview renders OSC 8 links, styled underlines and
  follows color-scheme reports.

Also includes the inspector's integration edits in shared files
(renderer state hook, termio VT recording, core/apprt-gtk wiring), X1's
config/input/cli additions for completion generation, and a fix for a
race in the termio backpressure test (it wrote before `stty raw`
applied, so the cooked line discipline dropped bytes past MAX_CANON).

Test Plan:
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings

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

@@ -975,6 +975,13 @@ impl Surface {
     ) -> Result<bool, CoreError> {
         let cfg = self.cfg();
 
+        // If we have an inspector, we always queue a render
+        let _inspector_render = self
+            .inspector
+            .borrow()
+            .is_some()
+            .then(|| RenderOnDrop(self));
+
         // Always record our latest mouse state
         let hidden = {
             let mut m = self.mouse.borrow_mut();
@@ -1915,6 +1922,10 @@ impl Surface {
         // The mouse position in the viewport
         let pos_vp = self.pos_to_viewport(f64::from(pos.x), f64::from(pos.y));
 
+        // If we have an inspector, we need to always record position
+        // information
+        self.inspector_record_cursor_pos(f64::from(pos.x), f64::from(pos.y));
+
         // We always reset the over link status because it will be
         // reprocessed below. But we need the old value to know if we need to
         // undo mouse shape changes.
@@ -2217,6 +2228,15 @@ fn button_from_index(i: usize) -> Option<MouseButton> {
     })
 }
 
+/// Queues a render when dropped (Zig: `defer self.queueRender()`).
+struct RenderOnDrop<'a>(&'a Surface);
+
+impl Drop for RenderOnDrop<'_> {
+    fn drop(&mut self) {
+        self.0.queue_render();
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;