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-renderer/src/state.rs

@@ -22,11 +22,11 @@ pub struct State {
     /// The terminal data.
     pub terminal: Terminal,
 
-    /// The overlay features currently requested by the terminal inspector
-    /// (Zig: `inspector: ?*Inspector` and `inspector.rendererInfo()
-    /// .overlayFeatures()`). Empty while the inspector is not active.
-    // TODO(integration): the inspector is deferred (Phase 7); it fills this.
-    pub overlay_features: Vec<OverlayFeature>,
+    /// The terminal inspector, if any (Zig: `inspector: ?*Inspector`). This
+    /// is `None` while the inspector is not active. It is accessed under the
+    /// same lock as the terminal (lock order: this state, then the
+    /// inspector's own lock).
+    pub inspector: Option<Arc<dyn InspectorHook>>,
 
     /// Dead key state. This will render the current dead key preedit text
     /// over the cursor. This currently only ever renders a single codepoint.
@@ -39,6 +39,20 @@ pub struct State {
     pub mouse: Mouse,
 }
 
+/// The view of the terminal inspector that the renderer and termio need
+/// (the inspector crate itself depends on this crate, so the Zig
+/// `*Inspector` pointer is expressed as a trait object).
+pub trait InspectorHook: Send + Sync + std::fmt::Debug {
+    /// The overlay features requested in the inspector's renderer window
+    /// (Zig: `inspector.rendererInfo().overlayFeatures()`).
+    fn overlay_features(&self) -> Vec<OverlayFeature>;
+
+    /// Record data read from the pty before it is processed by the terminal
+    /// (Zig: `Inspector.recordPtyRead`). Termio calls this one byte at a
+    /// time while an inspector is active.
+    fn record_pty_read(&self, t: &Terminal, data: &[u8]);
+}
+
 /// The shared, mutex-protected renderer state.
 pub type SharedState = Arc<Mutex<State>>;
 
@@ -46,7 +60,7 @@ impl State {
     pub fn new(terminal: Terminal) -> State {
         State {
             terminal,
-            overlay_features: Vec::new(),
+            inspector: None,
             preedit: None,
             mouse: Mouse::default(),
         }