v0.3.0

Newly refused flag values. --pages 0, --concurrency 0 and any
negative --pages, --concurrency, --delay, --retry-delay or
--proxy-block-retries are now usage errors (exit 2) naming the flag, in
every engine and in scraper_api_client.py. They used to be accepted: a
zero page count fetched nothing and reported an empty catalogue, and a
negative pause crashed the run after page 1.

pyppeteer, a page that never loads, no --proxy: the run now ends as a
load failure (exit 5, or 6 with rows) instead of a traceback and exit 1.
With a pool, a repeated timeout no longer rotates the exit; only an
unusable exit does, as in the other engines.

Fixed

• pyppeteer crashed with AttributeError when a page failed to load and
  no proxy was configured. The load-failure branch called
  pool.advance(...) on a None pool. It now rotates only for an unusable
  exit, and only when the pool has another exit to rotate to.
• The per-page solve allowance was spent by a detection that bought
  nothing. The pre-classification captcha check used up the page's one
  solve even when it found no challenge, so a challenge first seen after
  classification was never offered to the solver and the page was reported
  as blocked. The allowance is now claimed immediately before the paid
  request, in all three browser engines. A purchase that fails still counts,
  so the cap still holds at one per page across retries and rotations.
• The credential scan read nothing from a clone under a directory named
  build or dist. The skip list was tested against the absolute path. It
  now tests the path relative to the repository, a scan that reads zero
  files fails, and .env* backups, .json and .csv files are read too.
• .gitignore now covers every --dump-html NAME --pages N output
  (NAME.pageN), a root-level *.html dump and the usual working
  directories (live/, out/, tmp/, ...).
• .env.example ships KOSE_URL commented out, so a copied .env does not
  decide what a run fetches.
• The canary's Scraping Browser job no longer passes by skipping: with no
  KOSE_CDP_ENDPOINT secret it fails with an error naming the secret, and an
  exit 5 over CDP is a failure rather than a warning.
• Comments that named columns this schema does not have, stated a category
  total as current, carried another vendor's wording or gave the wrong exit
  code for parser_found_nothing (it is 5) were corrected; the CI sample
  summary counts priced rows instead of a column that does not exist.
• Shipped files, including the README, --help output and the 0.1.1 notes
  below, no longer cite private notes by name or section number; a suite
  check keeps it that way.
• smoke_test.py -v no longer crashes on a check whose detail is not a
  string.