Fix version field inconsistency in Sources.json

Problem: version field is inconsistent across entries:

• Some have semantic version (e.g., kerykeion: "4.26.0")
• Some have SHA as version (e.g., clay: "cc7729b1...")
• Some are missing version entirely

Solution (Option A - Two fields):

• version = semantic version (optional, for humans)
• rev = git SHA (required, for nix reproducibility)

Changes needed:

1. Fix clay: remove SHA from version field (or find real version)

2. Add missing version where derivable from rev tag:

• interegular: version="0.2.1" (from rev "v0.2.1")
• outlines: version="0.0.8" (from rev "0.0.8")
• perscache: version="0.6.1" (from rev "0.6.1")

3. Update Nix helpers to handle missing version gracefully: nix version = src.version or (builtins.substring 0 8 src.rev);

4. Entries that don't need version (infrastructure):

• nixos-* entries (not packages)
• niv, nvidia-patch-nixos, nixos-mailserver

Files: Omni/Bild/Sources.json, Omni/Bild/Functions.nix