LA-00: Establish the green source baseline #94

Part of #84.

Owner: Anders (@andersalm).

Status: Done. Accepted source ecda431dd194ce073072031a027cdf5b233d56ba, tree 5ec6cd29bf1e6a6500d70c042768e2f997338a23.

Done means

Release acceptance: Each exposed feature works clearly from start to end, including recovery. Keep unfinished or confusing features hidden until their complete journey passes. Hiding a feature does not complete its task; source checks alone do not establish installed acceptance.

• Strict source, lint and test checks pass.
• Source-home checks pass on Mac, Linux x86-64 and Linux ARM64.
• The accepted source and CI result are recorded in PR #72 and run 36508466892.

This establishes the source baseline. Installed product acceptance belongs to the later target tasks.