Rewritten because build_mapview.py imports navmap. This is what tracking
a .pyc costs - it will churn whenever a tool that imports navmap runs,
without ever being a source change. One .gitignore line ends it.
Everything outstanding, uncurated: the bytecode cache Python wrote beside
navmap.py while building the pages. It is derived from a tracked source
and tagged to one interpreter (cpython-314), so it will go stale rather
than break anything - one .gitignore line drops it again if it becomes
noise.