Commit a gas/instruction snapshot and diff it in CI

[Jaydbrown]

Generate per-entry-point CPU-instruction counts, commit the snapshot, and post the delta on each PR so cost regressions are visible in review.

[abdulrahamza]

Hi, I'll like to look into this and deliver quality and productive PR

[ZacLou]

I'd like to work on this issue. I have relevant experience with this tech stack and can deliver a clean, well-tested PR. I can submit within 1-2 days.

[ZacLou]

I'd like to work on this — opened a PR at #522.