Package 0.90.0 — three fixes

Three fixes ship and no schema moves, so core and the three packs stay at 0.65.0 and the package moves to 0.90.0 with both reusable workflows' refs.

• A frontmatter field declared ref → <type> or ref? → <type> that is written as a YAML list, block or inline, is refused under R9: a reference names one entity. array of ref → is unchanged (#330, #335).
• A repeated --pack on init and upgrade accumulates as if written --pack a,b; the usage text says the flag is repeatable (#331, #336).
• A type's row may declare notSelf: { section, column }, a reference column of a table that never names the page it is on; the landscape pack's system declares it for ## Connects to, so a system cannot connect to itself (#332, #334).

What breaks. Nothing. An instance that wrote a scalar reference as a list of two now hears so; none of the family's instances did.

How to take it. Move the pin to v0.90.0 and run companygraph upgrade, which changes nothing in the instance; the checker and the CLI carry the three fixes.

Verified: npm run verify with its release check, typecheck, build:check and every test:* script pass, as do conventions-format and conventions-check.