v0.52.0 — a judgment endpoint as a skill, not a tool

A judgment endpoint as a skill, not a tool. BlockRun now serves
POST api.blockrun.ai/v1/decide — typed yes/no, labelled-choice and
scored-rung judgments over a text or JSON state, served by OpenJev, free
behind a registered key. The obvious move was a blockrun_decide tool. It was
not made: every caller of this server is already a frontier model and a better
one-off judge than a 4B NLI cross-encoder, the default install is a wallet with
no key, and a tool taxes every user's context on every turn for an experiment
few run. The endpoint earns its place when someone wants one fixed ruler over
many items, or is prototyping a judgment they will later run from a pipeline
without a model — and that is a curl recipe, which is what a skill is for.

Skills

• feat(skills) — decide. The seventeenth skill: the request shape, the
  three question types and their limits (1–64 questions, 2–255 criteria), the
  response, an eval loop over the user's own labelled rows, and the errors. Two
  things it says because every surface has to: the confidence on a choice is
  a share of the agreement found, not the probability the answer is correct
  (equal-weak and equal-strong support are indistinguishable once the scores
  are normalised), and OpenJev is not Jev — unaffiliated, MIT, no published
  comparison and none invented. It also tells the agent to export the key in
  the shell rather than write ~/.blockrun/.api-key, because that file moves
  every paid tool to account billing at the next start.
• docs — the router skill points a fixed-ruler question at decide, and
  the README, CONTRIBUTING and setup skill count seventeen.

Nothing in src/ changed: the tool count, the schema cost and every price
table are as they were in 0.51.1.