v0.7.1

Everything in this release is in notary/ and in CI. The lethe package is
unchanged from 0.7.0 — git diff v0.7.0..v0.7.1 -- lethe/ is empty — so there
is nothing to gain by upgrading lethe-delete itself. Upgrade if you run the
notary: as declared, it could not take a payment on a clean install.

Fixed

• lethe-notary declared x402>=2 but the payment path needs x402[evm]
  and x402[httpx]. A clean install started the service and could not take a
  payment. Measured on a clean venv: bare x402 raises ImportError from
  x402.mechanisms.evm.exact.register ("EVM mechanism requires ethereum
  packages"), and x402[evm] without httpx fails preflight with "No module
  named 'httpx'". Invisible locally, where eth_account, eth_utils and
  httpx all arrive transitively. Missing eth_utils additionally disabled
  the EIP-55 checksum on LETHE_NOTARY_PAY_TO in silence — confirmed by
  feeding it an address with one wrong character, which it accepted.
• lethe-notary[dev] declared httpx2, which is a real distribution that
  ships a module named httpx2. Starlette's TestClient imports httpx. The
  tests passed only because httpx arrived transitively; a clean install of the
  extra could not import TestClient at all.
• notary/tools/pay.py overwrote the previous receipt. A fixed
  receipt.json meant buying a second certificate destroyed the first
  receipt — the artifact the tool's own output calls "the evidence". Measured:
  two purchases left one file. Receipts are now named after the certificate's
  payload hash, and a differing receipt at that path is refused rather than
  replaced. Re-running the same certificate rewrites an identical file, so the
  idempotency check stays a two-command exercise.
• pay.py crashed with a bare KeyError on a 402 carrying no
  PAYMENT-REQUIRED header — a stripped header or a URL that is not a
  notary. It now says which, and exits 2.
• PaymentGate.charge returned tuple[bool, object | None], and an
  object in the return position meant a type checker could see nothing about
  its callers — including the three route handlers whose bodies mypy was
  therefore skipping entirely. It now returns either the response to send or
  the settlement record, so the two outcomes are distinguishable by type.
  Checking those bodies immediately surfaced six unnarrowed values in
  /witness, where all(isinstance(v, str) for v in ...) validates at runtime
  but narrows nothing.

Added

• notary/ is now covered by CI: ruff, mypy, its own test run, and a
  no-extras install job that imports the whole paid path and quotes a price.
  It was checked by hand for three releases, which is another way of saying
  nobody was checking. Dependabot now watches notary/pyproject.toml too.
• The notary says whether it is charging real money. network_kind()
  classifies a CAIP-2 id as testnet, mainnet or unknown — never guessing,
  because assuming either way is unsafe in a different direction. The startup
  banner and /.well-known/notary both report it, so an operator one
  environment variable away from mainnet, and an agent deciding whether to pay,
  can both tell.
• notary/tools/pay.py — the buyer side of the x402 flow. It exists to be
  run twice: the second run of the same certificate must report
  charged: false and settle nothing, which is the idempotency guarantee the
  payment design rests on.
• The skipped-test guard in CI now covers the notary's suite as well, and fails
  on a missing report rather than passing over a run that never happened.
• Two tests for the settlement reference the notary hands back — the payer's
  only independent proof the money moved. v0.7.0 fixed the bug that discarded
  it, but the fix was guarded only by live-marked tests that CI never runs:
  dropping the payment block from either the normal response or the
  witness-write-failure response left the whole offline suite green.