docs(debugger): correct trace-frame op name and sx_trace_push attribution (A9.2)

Name the niladic op `.trace_frame` (no `.trace_frame_push` op exists) in
the trace-path roadmap, matching the rest of the doc and src/ir/inst.zig.
Describe the `.trace_frame` arm as building/interning the Frame global and
yielding its address as the op's value; the separate sx_trace_push call is
emitted by the lowerer via normal call lowering, not by the arm itself.

docs/debugger.md

@@ -109,8 +109,9 @@ each backend derives the frame from its own context:
   current function → `{file, line, col, func}` (reusing the source map
   wired in for DWARF), **interns and builds the `Frame` global** in
   [`src/backend/llvm/reflection.zig`](../src/backend/llvm/reflection.zig)
-  (the same mechanism, in the same file, as the tag-name table), then emits
-  `call sx_trace_push(ptr)`.
+  (the same mechanism, in the same file, as the tag-name table), and yields
+  its address as the op's value. The lowerer feeds that value to a separate
+  `sx_trace_push` call emitted through the normal call lowering.
 - **`interp`:** pushes the packed `(func_id, ir_offset)` from its own
   execution context.
 
@@ -276,13 +277,15 @@ traces and DWARF can never disagree:
 
 1. `lower.zig` reaches a failure site — `lowerRaise`, `lowerTry`'s
    propagation branch, `lowerFailableOr`, or `lowerDestructureDecl` — and
-   (when `tracesEnabled()`) emits the niladic `.trace_frame_push` op,
-   replacing today's `emitTracePush(placeholderTraceFrame())`. Absorbing
-   sites emit `emitTraceClear()` → `call sx_trace_clear()`.
-2. **Compiled backend** (`emit_llvm.emitInst`, `.trace_frame_push` arm):
+   (when `tracesEnabled()`) emits the niladic `.trace_frame` op via
+   `placeholderTraceFrame()`, whose result feeds a separate `sx_trace_push`
+   call via `emitTracePush()`. Absorbing sites emit `emitTraceClear()` →
+   `call sx_trace_clear()`.
+2. **Compiled backend** (`emit_llvm.emitInst`, `.trace_frame` arm):
    resolve the op's `span` + current function → `{file,line,col,func}`,
    intern into the `Frame` table (built alongside `tag_name_array`), and
-   emit `call sx_trace_push(ptr_to_Frame)`. The `sx_trace_push` extern is
+   yield the `Frame` global's address as the op's value, which the separate
+   `sx_trace_push` call (step 1) consumes. The `sx_trace_push` extern is
    declared lazily by `getTraceFids()` (which sets `needs_trace_runtime`).
 3. **Interpreter** (`interp.zig`, same op): pack `(current_func_id,
    ir_offset)` into a `u64` and call the foreign `sx_trace_push` (resolved