Refactor FFI analytics to track only successful completions

Move analytics.Features.ffi increments from internal compile functions
to the JS host function return points. This ensures we only count FFI
usage when operations successfully complete and return to JavaScript:

- dlopen (FFI.open): Increment after library loads and symbols compile
- TCC compile (Bun__FFI__cc): Increment after C code compiles successfully
- Callbacks (FFI.callback): Increment after callback wrapper compiles

Removed increments from internal helpers (CompileC.compile,
Function.compile, Function.compileCallback) to avoid double-counting.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/analytics.zig

@@ -87,6 +87,7 @@ pub const Features = struct {
     pub var yarn_migration: usize = 0;
     pub var pnpm_migration: usize = 0;
     pub var yaml_parse: usize = 0;
+    pub var ffi: usize = 0;
 
     comptime {
         @export(&napi_module_register, .{ .name = "Bun__napi_module_register_count" });

src/bun.js/api/ffi.zig

@@ -802,6 +802,8 @@ pub const FFI = struct {
         bytes_to_free_on_error = "";
         compile_c.symbols = .{};
 
+        bun.analytics.Features.ffi += 1;
+
         const js_object = lib.toJS(globalThis);
         jsc.Codegen.JSFFI.symbolsValueSetCached(js_object, globalThis, obj);
         return js_object;
@@ -851,6 +853,7 @@ pub const FFI = struct {
             .compiled => {
                 const function_ = bun.default_allocator.create(Function) catch unreachable;
                 function_.* = func.*;
+                bun.analytics.Features.ffi += 1;
                 return JSValue.createObject2(
                     globalThis,
                     ZigString.static("ptr"),
@@ -1149,6 +1152,8 @@ pub const FFI = struct {
             .functions = symbols,
         });
 
+        bun.analytics.Features.ffi += 1;
+
         const js_object = lib.toJS(global);
         jsc.Codegen.JSFFI.symbolsValueSetCached(js_object, global, obj);
         return js_object;