Build the Themes Tool

The themes shape surfaces what nobody named. Read its spec first - docs/theme-format.md - then build skill/scripts/themes.py: the pipeline and renderer are given; the projectionAn in-memory copy of part of your database that graph algorithms run against. You choose which nodes and relationships it holds. query is marked BUILD FROM SPEC.

This completes Building Block 2: "Themes nobody named exist as data" ✓