Setup only — do NOT build shared books yet, that is the next task.

This part continues the product you already built — the ledger,
receipts, several currencies, and crypto beside the cash.

Same repository, same documented commands. If you are starting in an
empty folder, your earlier work is fetched for you before you begin.

Before writing anything new, check that what you carried in still stands:

• AGENTS.md still declares stack:, run: and test:;
• the suite the test: line names is green;
• the parts already delivered are still delivered.

And check the product itself, not only its suite. These must still be true
of what you carried in:

• the ledger, receipts and the foreign-currency reporting of the earlier
  parts still hold
• 0.01750000 BTC bought on 2026-03-02 still cost 1071.70, is worth
  1030.75 on 2026-03-20, and reads -40.95 unrealised
• eight decimals still survive a round trip through the product

Fix whatever the hand-over broke before you start this part — a judge reads
the product on this rung, and everything the earlier parts earned is judged
again at the end of it, so a regression carried in quietly costs twice.

Money is rarely one person's. The product opens up: a book several people
share, entries that remember who paid, debts that follow from that, and
permissions that actually hold. You decide when it is done; a judge panel
scores the result.

The people in the scenarios below, and what they may do with the household
book:

Scenarios:

Scenario: A book is shared
When Ada shares the household book with Grace as an editor
Then Grace finds it among her books and can record an entry in it

Scenario: Private stays private
Then Ada's own book is invisible to anyone she has not shared it with
And nothing Grace does reaches it

Scenario: Every entry has an author
When Grace records the grocery run
Then the entry says it was Grace who recorded it, and who paid for it

Scenario: Splitting a bill
When Ada pays 84.00 for groceries and splits it evenly with Grace
Then Grace owes Ada 42.00
And both of them can see that this is so

Scenario: Settling up
When Grace settles the 42.00
Then nobody owes anybody
And the settlement is itself part of the book's history

Scenario: A viewer cannot edit
When Linus tries to change an entry
Then the product refuses him
And it refuses him even when the buttons are not on the screen

Scenario: Leaving the book
When Ada removes Grace from the household book
Then Grace loses access
And the entries Grace recorded stay where they are

Everything beyond the scenarios is yours: how people sign in, how an
invitation travels, what a shared book looks like next to a private one.

When you are done, write .ololo/money-tracker-people-done.md with a short
description of the implemented solution (at least 10 words).