fix(interop): re-vendor Pelorus with the x265 CSV column indices initialised (HISS-10)

[lusoris]

BLUF: the vendored pelorus_qp_report_csv.c gave seven -Wmaybe-uninitialized warnings at gcc 16 -O2 -Wall -Wextra; the cause is fixed in VMAFx/pelorus and re-vendored here. HISS-10 (zero warnings) binds vendored code.

• Cause: csv_cols cols in x265_csv_read_rows() was uninitialised until the header row. Fixed upstream in VMAFx/pelorus#79 (merge 42cb17106a2d): every index starts at -1 (absent), no pragma.
• Here: PELORUS_VENDOR_SHA moved, mirror re-rendered by scripts/sync-pelorus-interop.sh --update; --check reports no drift.
• Warnings: 7 before (type, poc, qp, bits, psnr_y/u/v), 0 after, gcc 16.2.1 -std=c11 -O2 -Wall -Wextra. test_pelorus_interop passes.
• CI gap: no vmafx lane builds with -Werror (core/meson.build sets warning_level=2 only). Recorded in the state row; not changed here.
• tidy: exact Pelorus mirror files are excluded from the clang-tidy lanes by scripts/ci/pelorus-mirror-paths.txt; the lane refuses them as TUs.

Reproducer: scripts/sync-pelorus-interop.sh <pelorus checkout>; gcc -std=c11 -O2 -Wall -Wextra -Icore/include -Icore/src -c core/src/interop/pelorus_qp_report_csv.c -o /dev/null

• Research digest — no digest needed: trivial
• Decision matrix — no alternatives: only-one-way fix
• AGENTS.md invariant note — no rebase-sensitive invariants beyond the existing mirror rule
• Reproducer / smoke-test command: above
• CHANGELOG fragment: changelog.d/fixed/pelorus-qp-csv-cols-initialised.md
• Rebase notes: docs/rebase-notes.md entry
• docs/state.md: row opened and closed by this PR
• ADR: not needed, bug fix
• User-facing docs: no user-visible surface change (pin text in docs/api/pelorus-interop.md updated)