ci(*): add build/test app scripts, workflow

[vdice]

Alternative to #65

• Adds GH workflow to run parallelized app builds (reduces time from ~15 mins (in ci(*): test samples and tutorials #65) to just over 2 mins)
• Adds a preliminary test script -- but too large a number of apps require specific testing, so holding off on adding to CI until we come up with a plan there (if we ever want to)
• Adds a few setup Make targets for apps that require a bit of prep before building or running

Sample run: https://github.com/vdice/fwf-examples/actions/runs/16647598287

(Not sure why the checks aren't showing -- maybe the workflow needs to merge first. Here's a sample PR on my fork with the checks: vdice#3 recent workflow run on my fork: https://github.com/vdice/fwf-examples/actions/runs/19577160467)

[mikkelhegn]

@vdice You want to go ahead with getting CI testing set up?

[vdice]

@vdice You want to go ahead with getting CI testing set up?

I'd propose we get this first change set in which adds build automation for all apps to CI plus a sketch of what testing the apps might look like. Then work on testing in a follow-up. Just getting automated builds would be a great first step. What do y'all think?