Speed up fork CI feedback loop

[baby-joel]

Problem

KKL/pi CI is slow enough to interrupt the fork-maintenance loop. The current CI runs a full build/check/test sequence on every PR and main push:

• npm ci --ignore-scripts
• system deps install
• npm run build
• npm run check
• npm test

For sync/release PRs this is valuable, but for small workflow/version-only PRs the feedback cycle feels heavy.

Possible improvements

• Split CI into separate jobs (build, check, package test jobs) so failures surface earlier and jobs run in parallel.
• Cache system/native dependency setup where possible.
• Add path-based lighter checks for workflow-only or docs-only changes.
• Consider a required fast lane plus an optional/manual full suite for release/sync PRs.
• Investigate which package tests dominate runtime and whether they can be parallelized further or isolated.

Constraints

• Do not weaken release confidence: upstream-sync and KKL release PRs should still get full validation before merge/release.
• Keep fork CI simple until the release process is stable.

[rikonor]

you know what? maybe i was overly harsh... it took two minutes, that's not that bad. i feel bad about that issue
now.