docs: start a findings log

[Madeuss]

A place for what surprised us, so it survives long enough to be written about.

Why

The details that make a write-up worth reading are the ones that evaporate
first. Nobody will remember why the evidence fact pointed at the wrong person,
or that a PREPOSICAO map once sat inside the case generator. Those are the
entries; the successes mostly document themselves in the ADRs.

Format is deliberately strict: what happened, why it matters, a link. If it
surprised nobody, it is not a finding — it is a changelog line, and it does not
go here.

What it starts with

Everything phase 1 produced, including the parts that were mistakes:

• the validator catching two generator bugs on day one, both of which read as
  correct code
• Portuguese grammar leaking into the domain model
• a downside written into ADR-0007's consequences and then left in place for
  days — documenting a cost feels like addressing it
• half a turn's worth of GitHub behaviour learned by tripping over it: a ruleset
  that was inert on a private repo while showing as active, a branch rename that
  closes the PRs whose head it renamed, a merge box that freezes the commit
  message when the page loads
• the economics of per-token versus per-hour billing, with the measured prompt
  size behind it

It also carries two ideas the work threw off: an automated detective as an
eval — an agent that plays a match with only what a player can see, proving in
practice what the solver proves structurally — and a comparison of open-weights
models served from a Brazilian cloud against the adversarial suite, in
Portuguese.

Cost of keeping it

One line per discovery, written when the discovery happens. The project's own
principle is that a document which does not pay rent is debt — this one pays by
being the skeleton of the article and by stopping the same mistake twice.

85 passed · ruff clean · mypy strict