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

Cargo.toml

@@ -14,6 +14,7 @@ ghostty-config.workspace = true
 ghostty-apprt-gtk.workspace = true
 ghostty-apprt.workspace = true
 ghostty-cli.workspace = true
+ghostty-os.workspace = true
 log = "0.4"
 
 [lints]
@@ -23,6 +24,11 @@ workspace = true
 resolver = "3"
 members = [".", "crates/*"]
 
+# The upstream Ghostty version this rewrite tracks (Zig: `build.zig.zon`
+# `.version`); consumed by `crates/ghostty-cli/build.rs`.
+[workspace.metadata.ghostty]
+app-version = "1.3.1"
+
 [workspace.package]
 version = "0.1.0"
 edition = "2024"
@@ -38,12 +44,14 @@ ghostty-font = { path = "crates/ghostty-font" }
 ghostty-renderer = { path = "crates/ghostty-renderer" }
 ghostty-termio = { path = "crates/ghostty-termio" }
 ghostty-os = { path = "crates/ghostty-os" }
+ghostty-onig = { path = "crates/ghostty-onig" }
 ghostty-datastruct = { path = "crates/ghostty-datastruct" }
 ghostty-core = { path = "crates/ghostty-core" }
 ghostty-apprt-gtk = { path = "crates/ghostty-apprt-gtk" }
 ghostty-apprt = { path = "crates/ghostty-apprt" }
 ghostty-cli = { path = "crates/ghostty-cli" }
 ghostty-bench = { path = "crates/ghostty-bench" }
+ghostty-inspector = { path = "crates/ghostty-inspector" }
 
 [workspace.lints.rust]
 unsafe_code = "forbid"