ERR/E3.0 (slice 3b): comptime trace resolution

#run failures now print the same `func at file:line:col` trace as
runtime, resolved in-process via the interpreter's IR/source tables.

- Read-side context-split op `.trace_resolve` (mirror of .trace_frame),
  lowered from a name-recognized `__trace_resolve_frame(u64) -> Frame`.
- emit_llvm: inttoptr the operand to *Frame + load (the value
  .trace_frame stamped in).
- interp: unpack (func_id << 32 | span.start); resolve func/file from
  module.functions and line/col via SourceLoc.compute over a new
  source_map (setSourceMap wired at every production interp site).
- trace.sx: frame_at -> u64; to_string routes each frame through
  __trace_resolve_frame, so one source works in both machines.

Compiled path behavior unchanged (243/244/247 identical; it now loads
via the op). New examples/253-comptime-trace.sx exercises the comptime
path. Gates: zig build, zig build test, run_examples.sh -> 291 passed.

src/core.zig

@@ -180,6 +180,7 @@ pub const Compilation = struct {
         const mod = self.ir_module orelse return error.NoIRModule;
         var interp = ir.Interpreter.init(mod, self.allocator);
         defer interp.deinit();
+        interp.setSourceMap(&self.import_sources);
         if (self.ir_emitter) |*e| interp.build_config = &e.build_config;
         ir.Interpreter.last_bail_op = null;
         ir.Interpreter.last_bail_builtin = null;