[MathurAditya724]

Accept optional parameter JSDoc on JavaScript setters whose executable parameter is mandatory. Generated bindings can document undefined without scriptc treating the comment as an optional setter parameter. Real optional/default/rest syntax, caller type checks, and reflective argument-count restrictions retain their existing diagnostics.

A preflight-owned index collects attached JSDoc spans once per SourceFile and uses binary containment lookup. SourceFile identity keeps original and rewritten JSX snapshots separate when they share a filename. Regression coverage includes checked JavaScript, syntax negatives, native setter behavior, JSX offsets, and traversal growth for many setters.

Independent stock artifact and quiet timing runs against the main snapshot used by this branch passed. They cover 5,380 identical IR/LLVM/native executable comparisons, three additional identical compiler/emitter LLVM comparisons, 126 unchanged baseline refusals, and the new setter fixture. All 59 benchmark artifact hashes also match across the separate runs. The compiler's own source passes its heap, output-growth, dynamic-tier and compile-cost budgets.

Compilation measurements use Node 24.22.1 on Darwin arm64 and the stock 300-pair protocol. The 95% intervals remain below the 2% growth threshold; the self row has only one pair and no meaningful confidence interval.

Workload	Change	95% interval
59 benchmarks, five pairs each	+0.06%	+0.005% to +0.21%
Compiler self-build, one pair	-0.02%	Single sample
Two emitter fixtures, two pairs each	-0.18%	-0.44% to +0.08%

Fixes #3355.

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