test(pargates): --budget-scale F scales the DEFAULT gate budget; CI passes 4 — the flat 300 s cap was a 3-8x-multiplied tripwire on sharded runners

paginationcheck (53 s local) hit rc=124 at exactly 300.0 s on main run 34151288379's plain clang shard 2/4, one
run after mcpframehonestycheck did the same; 64 uncapped gates sit inside the runner multiplier of the cap, so
per-gate entries are the wrong shape and raising the constant would blunt the tripwire locally. Explicit
GATE_BUDGET_SEC entries (CI-derived) are untouched; the TIMEOUT message names the effective budget and scale.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>