Docs: Record the notebook decisions in INTENT and move M2 earlier #17

The maintainer settled three INTENT §4 questions (declared app root with no update function, quoted verbatim; Column/Row/Spacer also from material3; both Alignment spellings). Record them as INTENT §5 and point SPEC and PROJECT.md at it. The Gradle cache was never broken, so M2 moves from 2026-11-13 to 2026-11-06 and M3 from 2026-11-27 to 2026-11-20. Done when the documents agree, check_guide reports 0 findings, and test counts are unchanged.