feat(vt-capi): port the libghostty-vt C API

Ports ZIG/src/lib_vt.zig and terminal/c/* as crates/ghostty-vt-capi
(cdylib + staticlib + rlib, soname libghostty-vt.so) implementing the
unchanged include/ghostty/vt.h + vt/*.h ABI: OSC parser, SGR parser,
key events and key encoding, paste safety, colors, result codes - all
38 native symbols, plus the ghostty_wasm_* helpers on wasm32.

Verification:
- tests/abi.rs generates a C probe from the headers, compiled with cc,
  that checks sizeof/alignof/offsetof of every struct/union, every
  enumerator and #define against Rust, and links every declared symbol;
  nm -D exports equal the declared functions.
- Ghostty's example/c-vt* programs compile unchanged against the Rust
  library (shared and static) and produce the expected output.
- The wasm32 build runs Ghostty's wasm-key-encode/wasm-sgr example
  scripts unmodified under node (upstream's wasm-sgr tag table is stale
  vs sgr.h; a regenerated copy checks full output).

Test Plan:
- cargo test -p ghostty-vt-capi (22 unit + 2 ABI + 5 C + 3 wasm tests)

crates/ghostty-vt-capi/examples/c/c-vt.c

@@ -0,0 +1,36 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <ghostty/vt.h>
+
+int main() {
+  GhosttyOscParser parser;
+  if (ghostty_osc_new(NULL, &parser) != GHOSTTY_SUCCESS) {
+    return 1;
+  }
+  
+  // Setup change window title command to change the title to "hello"
+  ghostty_osc_next(parser, '0');
+  ghostty_osc_next(parser, ';');
+  const char *title = "hello";
+  for (size_t i = 0; i < strlen(title); i++) {
+    ghostty_osc_next(parser, title[i]);
+  }
+  
+  // End parsing and get command
+  GhosttyOscCommand command = ghostty_osc_end(parser, 0);
+  
+  // Get and print command type
+  GhosttyOscCommandType type = ghostty_osc_command_type(command);
+  printf("Command type: %d\n", type);
+  
+  // Extract and print the title
+  if (ghostty_osc_command_data(command, GHOSTTY_OSC_DATA_CHANGE_WINDOW_TITLE_STR, &title)) {
+    printf("Extracted title: %s\n", title);
+  } else {
+    printf("Failed to extract title\n");
+  }
+  
+  ghostty_osc_free(parser);
+  return 0;
+}