v0.7.1

Nothing in the reader changed. This is a test that could fail on a busy
machine and a packaging manifest that had never been run, both found by
building the nix derivation for the first time.

Fixed

• Three watch tests no longer assert on their own setup. Creating the
  document is a write like any other, and arming the watch immediately
  afterwards does not reliably exclude it — the close can be reported once the
  watch is up. The negative test counted that as the failure it was looking
  for; worse, the two positive tests could pass on it, reporting a working
  watch without one. They now drain until the watcher goes quiet before
  asserting.

  It takes contention to see: 3 rounds in 20 of the suite inside the nix
  sandbox, 1 in 40 locally with four suites at once, and never on an idle
  machine — which is why three CI platforms called it green. concerns was
  never at fault, and no reader behaviour changes: the cost was always one
  redundant re-read of a document just opened, the bargain the sibling case
  already accepts on macOS.

• installManPage in the nix derivation was handed a named pipe. Process
  substitution is /dev/fd/63 — no name, no section suffix, and the hook
  declines to guess, so the install phase failed. The completions were
  unaffected because --cmd already names those.

• packaging/nix/README.md documented a command that could not work.
  default.nix takes lib and rustPlatform as arguments, so it needs
  callPackage, and a pinned nixpkgs rather than <nixpkgs>, which is a
  search-path error on an install with no channels.

Changed

• The nix derivation carries real hashes, and AGENTS.md records what a
  pty with no size looks like when the reader meets it: alternate screen
  entered, nothing painted, clean exit 0 — the size query working, not a
  broken binary.