fix(julia): verify compare-output targets and improve author recovery

[mstykow]

Summary

• Verify scorecard item 43 against compare-outputs on JuliaLang/Pkg.jl, JuliaLang/julia, and JuliaPlots/Plots.jl, then record the final Julia benchmark snapshots in docs/BENCHMARKS.md and mark the scorecard row verified.
• Support legacy singular Julia author metadata in Project.toml parsing and broaden author detection for Julia-flavored README/TOML patterns such as Created by, Original author, package-qualified Primary ... author, and inline author rosters with (@handle) suffixes.
• Tighten the follow-on author heuristics so code-shaped TOML snippets and generator banners stay quiet, and normalize original-author rosters into distinct people when the clean component detections exist.
• Saved compare artifacts under .provenant/compare-runs/20260419T082612Z-Pkg.jl-15780, .provenant/compare-runs/20260419T082612Z-julia-15784, and .provenant/compare-runs/20260419T082007Z-Plots.jl-7256.

Issues

• Covers: parser verification scorecard item 43 (Julia)

Scope and exclusions

• Included: targeted Julia parser metadata support, shared author-detection improvements needed by the Julia compare targets, refreshed compare-output snapshots, benchmark rows, the scorecard status update, and the minimal copyright-golden follow-up required by the shared detector changes.
• Explicit exclusions: no broad scanner refactors outside the Julia-driven author heuristics, and no target-specific benchmark-only tuning.

Intentional differences from Python

• Julia remains a Provenant-only parser family with no Python ScanCode parser reference, so verification here is based on common-profile repository comparisons and file-level triage rather than parser-to-parser parity.

Follow-up work

• Created or intentionally deferred: none.

Expected-output fixture changes

• Files changed: testdata/copyright-golden/copyrights/misco4/linux-copyrights/drivers/char/dtlk.c.yml, testdata/copyright-golden/copyrights/misco4/linux-copyrights/drivers/crypto/nx/nx-842.c.yml
• Why the new expected output is correct: the final detector keeps Original author: detections as distinct people instead of merged tails, so dtlk.c now preserves clean Chris Pallotta plus Jim Van Zandt, and nx-842.c preserves separate Robert Jennings and Seth Jennings. The surrounding heuristics were tightened so unrelated code-shaped authors = ... snippets and generator banners stay quiet, and the shared suites now pass locally with cargo test --features golden-tests copyright::golden_test::tests::test_golden_authors plus cargo test --features golden-tests copyright::golden_test::tests::test_golden_copyrights.