fix: close the tail items from the targeted re-audit

Resolves the 13 rows still partial in docs/rewrite/notes/review-rv4-
codex.md (details in final-Z5.md):
- Escaped config strings are decoded to raw bytes at every OS boundary:
  Flatpak cwd/argv to D-Bus, screen-file paths, the default config
  template, GHOSTTY_RESOURCES_DIR/TERMINFO/shell integration/
  bindtextdomain consumers, custom shader loading, list-themes hyperlinks.
- osbytes escapes literal U+FDD0 on non-Unix too (bijective everywhere);
  the GTK paste dialog only decodes text that was actually encoded.
- shadertoy: whole-array uses of iChannelTime rebuild a plain float[4]
  from the std140-padded members (naga-validated, MSL offsets checked).
- libghostty-vt: the OSC parser holds caller-allocated storage inline
  and command payloads borrow from it, so ghostty_osc_end performs no
  global allocations (verified from Rust and C).
- crash: aarch64 Linux minidump context fixed; macOS fatal signals record
  siginfo, registers and a fault-safe stack walk.
- tripwire: selectionString map allocation-failure cleanup test ported.
- libghostty-vt emits the versioned soname libghostty-vt.so.0 at build
  time (no patchelf needed at install).

Test Plan:
- cargo test --workspace (3342 passed)
- just check-macos; just check-macos x86_64-apple-darwin;
  just check-windows; just check-wasm
- cargo check --target aarch64-unknown-linux-gnu -p ghostty-crash

crates/ghostty-os/src/osbytes.rs

@@ -100,10 +100,18 @@ pub fn os_to_config_string(s: &OsStr) -> String {
     }
     #[cfg(not(unix))]
     {
-        s.to_string_lossy().into_owned()
+        valid_str_to_config_string(&s.to_string_lossy())
     }
 }
 
+/// Encode a string that is already valid UTF-8 (e.g. the WTF-8 to UTF-8
+/// conversion of a non-Unix OS string). The only thing that needs escaping is
+/// a literal escape character, so decoding stays a bijection on every
+/// platform. Shared (not cfg gated) so it is testable everywhere.
+pub fn valid_str_to_config_string(s: &str) -> String {
+    bytes_to_config_string(s.as_bytes())
+}
+
 /// Inverse of [`os_to_config_string`].
 pub fn config_str_to_os(s: &str) -> OsString {
     os_from_bytes(config_str_to_bytes(s))
@@ -142,6 +150,17 @@ mod tests {
         assert_eq!(config_str_to_bytes(icons), icons.as_bytes());
     }
 
+    #[test]
+    fn valid_str_encoder_escapes_literal_escape_char() {
+        // Shared logic of the non-Unix encoder: U+FDD0 U+00FF must not be
+        // mistaken for the escape of byte 0xFF.
+        let s = "a\u{fdd0}\u{ff}";
+        let e = valid_str_to_config_string(s);
+        assert_eq!(e, "a\u{fdd0}\u{fdd0}\u{ff}");
+        assert_eq!(config_str_to_bytes(&e), s.as_bytes());
+        assert_eq!(valid_str_to_config_string("plain"), "plain");
+    }
+
     #[test]
     fn literal_escape_char_is_doubled() {
         let s = "a\u{fdd0}\u{ff}";