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-apprt/Cargo.toml

@@ -9,6 +9,7 @@ ghostty-vt.workspace = true
 ghostty-input.workspace = true
 ghostty-config.workspace = true
 ghostty-datastruct.workspace = true
+ghostty-inspector.workspace = true
 ghostty-terminal.workspace = true
 ghostty-renderer.workspace = true
 thiserror = "2.0.21"

crates/ghostty-apprt/src/runtime_api.rs

@@ -242,11 +242,19 @@ pub trait CoreSurface {
         Err("screenshots are not supported".into())
     }
 
-    // ---- inspector (deferred) -------------------------------------------
+    // ---- inspector ----------------------------------------------------
+    /// `activateInspector`: begin collecting inspection data. This does not
+    /// affect the GUI, the runtime shows/hides the inspector UI itself.
     fn activate_inspector(&self) -> Result<(), CoreError> {
         Ok(())
     }
+    /// `deactivateInspector`: stop collecting inspection data.
     fn deactivate_inspector(&self) {}
+    /// `Inspector.render`: draw the inspector into the current Dear ImGui
+    /// frame (the main thread; called from the inspector widget's render).
+    fn render_inspector(&self, ui: &ghostty_inspector::imgui::Ui) {
+        let _ = ui;
+    }
 }
 
 /// Implemented by this crate (GTK `Application`); handed to core.
@@ -278,7 +286,7 @@ pub trait RtSurface {
     fn set_clipboard(&self, clipboard: Clipboard, contents: &[(String, String)], confirm: bool);
     /// `defaultTermioEnv`: env vars to set for the child (GDK/GTK related
     /// cleanups).
-    fn default_termio_env(&self) -> Vec<(String, String)>;
+    fn default_termio_env(&self) -> Vec<(std::ffi::OsString, std::ffi::OsString)>;
     fn redraw_inspector(&self) {}
     /// Resolve an OpenGL function pointer for the surface's GL context
     /// (GTK: dlsym on libepoxy). Called with the context current. Null if