feat(javascript): link assignment right-hand sides to their writes (#6206)

* feat(javascript): link assignment right-hand sides to their writes

A declaration carries its value forward, but a later assignment to a
variable, a property or through a compound operator stopped the forward
trace at the right-hand-side read. The semantic IR now records one
syntactic assignment flow per simple assignment target (ranges, operator,
owning callable), and the graph projection connects each retained read
of the right-hand side to the write occurrence through a defines
relation. Compound assignments also consume the previous value of the
target; the written value itself stays unknown, keeping the boundary of
#4342 intact.

Fixes #6193

* fix(javascript): preserve computed key assignment ownership

* test(javascript): retain nested callback assignment ownership

* docs(javascript): record assignment influence verification

* test(mcp): isolate mocks and acknowledge cancellation boundaries

* test(javascript): retain CLI diagnostics and current-main verification

---------

Co-authored-by: gensokyo-dev <342580529+gensokyo-dev@users.noreply.github.com>

src/application/javascript/JavaScriptSemanticGraphObjectProjection.ts

@@ -33,6 +33,10 @@ export function* projectSemanticObjects(
       operation,
       target.slotApplicability,
     );
+    if (occurrence !== null) {
+      if (operation.kind === "read") context.readNodes.push(occurrence);
+      if (operation.kind === "write") context.writeNodes.push(occurrence);
+    }
     const ends = objectRelationEnds(context, operation, occurrence, target);
     const resolved =
       operation.resolution === "complete" &&