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-input/src/binding/action.rs

@@ -1225,7 +1225,17 @@ impl ActionKey {
         }
     }
 
-    /// The doc comment of the action (Zig `help_strings.KeybindAction`).
+    /// The Zig `help_strings.KeybindAction` string: [`ActionKey::docs`]
+    /// without the single trailing newline every doc literal carries. (A
+    /// trailing empty `///` line in the Zig source is a second `\n`.)
+    #[must_use]
+    pub fn help_string(self) -> &'static str {
+        let d = self.docs();
+        d.strip_suffix('\n').unwrap_or(d)
+    }
+
+    /// The doc comment of the action (Zig `help_strings.KeybindAction`),
+    /// each literal ending in one extra newline.
     pub fn docs(self) -> &'static str {
         match self {
             ActionKey::Ignore => {
@@ -1438,6 +1448,7 @@ Valid arguments are:
 
     Adjust the selection to the beginning or the end of the line
     respectively.
+
 "##
             }
             ActionKey::JumpToPrompt => {
@@ -1468,6 +1479,7 @@ Valid actions are:
 
     The default OS editor is determined by using `open` on macOS
     and `xdg-open` on Linux.
+
 "##
             }
             ActionKey::WriteScreenFile => {
@@ -1574,6 +1586,7 @@ Valid arguments:
     Creates a new split along the larger direction.
     For example, if the parent split is currently wider than it is tall,
     then a left-right split would be created, and vice versa.
+
 "##
             }
             ActionKey::GotoSplit => {
@@ -1940,6 +1953,7 @@ The value determines the crash location:
   - `render`
 
     Crash on the render thread for the focused surface.
+
 "##
             }
         }

crates/ghostty-input/src/binding/mod.rs

@@ -498,10 +498,8 @@ pub const BACKWARDS_COMPATIBLE_KEYS: &[(&str, TriggerKey)] = {
 /// The codepoint we use for comparisons. Case folding can result
 /// in more codepoints so we need to use a 3 element array.
 ///
-/// DEVIATION: Zig uses uucode's full case folding table. Here we use
-/// `char::to_lowercase` (single-char results only) plus a few simple-folding
-/// special cases; multi-codepoint foldings return the codepoint as-is exactly
-/// like Zig does.
+/// Uses the full Unicode case folding table (uucode's `case_folding_full`,
+/// generated by `ghostty-unicode`).
 fn folded_codepoint(cp: u32) -> [u32; 3] {
     // ASCII fast path
     if let Some(c) = char::from_u32(cp)
@@ -511,24 +509,7 @@ fn folded_codepoint(cp: u32) -> [u32; 3] {
     }
 
     // Unicode slow path. Case folding can result in more codepoints.
-    // If more codepoints are produced then we return the codepoint
-    // as-is which isn't correct but until we have a failing test
-    // then I don't want to handle this.
-    let Some(c) = char::from_u32(cp) else {
-        return [cp, 0, 0];
-    };
-    // Simple-fold differences from lowercase.
-    match c {
-        '\u{00B5}' => return [0x03BC, 0, 0],
-        '\u{017F}' => return ['s' as u32, 0, 0],
-        '\u{03C2}' => return [0x03C3, 0, 0],
-        _ => {}
-    }
-    let mut it = c.to_lowercase();
-    match (it.next(), it.next()) {
-        (Some(l), None) => [l as u32, 0, 0],
-        _ => [cp, 0, 0],
-    }
+    ghostty_unicode::case_folding::fold_full(cp)
 }
 
 impl Trigger {

crates/ghostty-input/src/binding/tests.rs

@@ -1507,6 +1507,20 @@ fn trigger_hash_folds_case() {
     assert!(!uni('a').equal(&uni('A')));
 }
 
+#[test]
+fn trigger_full_unicode_case_folding() {
+    // Simple folds beyond to_lowercase: micro sign, long s, final sigma.
+    assert!(uni('\u{00B5}').folded_equal(&uni('\u{03BC}')));
+    assert!(uni('\u{017F}').folded_equal(&uni('s')));
+    assert!(uni('\u{03C2}').folded_equal(&uni('\u{03C3}')));
+    // Multi-codepoint full folds: capital sharp s folds to "ss", as does
+    // U+00DF itself.
+    assert!(uni('\u{1E9E}').folded_equal(&uni('\u{00DF}')));
+    assert_eq!(uni('\u{1E9E}').hash(), uni('\u{00DF}').hash());
+    // Non-equivalent codepoints stay distinct.
+    assert!(!uni('\u{00DF}').folded_equal(&uni('s')));
+}
+
 #[test]
 fn trigger_display_roundtrip() {
     for s in ["super+ctrl+alt+shift+a", "catch_all", "ctrl+arrow_up", "+"] {

crates/ghostty-input/src/helpgen_actions.rs

@@ -94,7 +94,7 @@ pub fn generate(writer: &mut String, format: Format, show_docs: bool) {
         }
 
         if show_docs {
-            let mut iter = key.docs().split('\n').peekable();
+            let mut iter = key.help_string().split('\n').peekable();
             while let Some(s) = iter.next() {
                 // If it is the last line and empty, then skip it.
                 if iter.peek().is_none() && s.is_empty() {

crates/ghostty-input/src/key.rs

@@ -1,7 +1,8 @@
 //! Key events and key codes (ZIG/src/input/key.zig).
 //!
-//! The Zig `imguiKey` helper (cimgui constants) is intentionally not ported;
-//! the inspector is deferred (see notes).
+//! The Zig `imguiKey` helper (cimgui constants) lives in the inspector crate
+//! (`ghostty_inspector::keys::imgui_key`) so that this crate stays free of
+//! the ImGui dependency.
 
 pub use crate::key_mods::Mods;