M3 puts a FAB nested in another component at level 0, and the documented pattern
puts one in the rail's header, so every documented use sat at elevation 3. The
rule is unlayered: the FAB's shadow is a utility and a layer would lose to it.
Plan: docs/plans/material-3-alignment.md, step 14 (navigation N-03).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9