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