One solve per page, CSV formula guard, parser failures and 404s reported, canary that must test the site

[jehrr]

Fixes from the 2026-10-14 audit of 8c653e3, plus the owner's canary requirement.

Behaviour changes

• A served listing whose payload names ads but parses to zero rows ends with stop_reason: parser_found_nothing → exit 5 (or 6 with rows from earlier pages). Before: exit 4 on page 1, a complete run (exit 0) on page 2+.
• --pages 0, --concurrency 0, negative --delay/--retry-delay/--proxy-block-retries (and in scraper_api_client.py negative --retries/--retry-delay, --timeout < 1) are usage errors (exit 2) naming the flag.
• CSV cells starting with = + - @ \t \r \n get a leading apostrophe (CSV only; JSON untouched; csv_cells_escaped in the sidecar, merged under the caller's extra).
• Canary: fails when DUBIZZLE_CDP_ENDPOINT is missing (named in ::error::), red on exit 3/5/6, red on a logged parser_found_nothing, weekly schedule added, no longer requires a merchandised "car of the week" row.

Fixes

Finding	Fix	Evidence
F1 solve budget bypassed	page_flow.SolveBudget, passed to both handle_captcha_if_present call sites in all three engines, allows()/spend() immediately before solve_recaptcha	Stubbed solver, forced challenge, no pool: 1 purchase per engine (audit measured 3). AST check + behavioural check per engine
F2 pyppeteer pool.advance on None	guarded with has_pool as Playwright does	stubbed failing goto, pool=None → load_failed, no exception
F4 CSV formula cells	_csv_escape after list/dict serialisation, strings only	=HYPERLINK(...) → '=HYPERLINK(...), -5.0 unchanged
F5 status dropped	Playwright/pyppeteer pass goto()'s status (reset to None after a solve reload); Selenium relies on product_parser.is_not_found_page (empty <title> + empty Redux action list: matches only the 404 among the 13 captures)	not_found fixture → empty in all three engines
F6 parser failure read as empty	PageOutcome.parse_failed, page_flow.failure_reason used by every stop-reason site	stubbed parser on motors_p1 → parser_found_nothing; finish_run → 5 / 6
F8 private citations	93 §N / private-file references reworded or removed; new suite guard (tokens assembled from pieces) over every tracked file. Release v0.1.0 notes checked: none	grep → 0
F9 other-site residue	search-grid/GraphQL/keyword=kopi/buy-box/scroll-count/2026-09-09 comments, umlaut URL docstring, mugs Docker example rewritten for this site	grep
F13 capture shapes	.gitignore + CAPTURE_SHAPES by kind (live/ out/ output/ run(s)/ result(s)/ tmp/ scratch/ dump(s)/, root *.html)	git check-ignore; intent-to-add live/dump.html → ci_checks.py --secret-check FAILED
F15 stale wording	README exit-5 line; smoke-test skip footer
F16 wording scan exempted the suite	banned phrases assembled from pieces, suite scans itself
CONTRIBUTING	dropped the unmeasured "credential does not survive a day" claim and the pointer to private notes
Metadata	description now says "2Captcha Scraping Browser API" (gh repo edit)

Verification

• Offline suite green in four venvs: core-only (528 PASS), +playwright (560), +pyppeteer (555), +selenium (548), each running its own engine's new fetch-path checks. No browsers downloaded; no network calls to 2captcha (solver stubbed) or the site.
• Planted-fault controls (PYTHONDONTWRITEBYTECODE=1, __pycache__ cleared), each RED on the named check, then restored green: CSV escape removed; budget.spend() removed (AST check in core, behavioural in selenium venv); pyppeteer guard removed; one _classify without status; is_not_found_page → False; parse_failed not set (playwright venv); --delay back to type=float; a § in README; a banned phrase in the suite; canary exit 3 not failing; canary parser grep disabled; missing-secret step not failing.
• ci_checks.py --all green.

Not changed

• Atomic writes (F3) and Python 3.13 in CI (F10): covered by Audit 2026-10-08: atomic output writes, Python 3.13 in CI #11, not duplicated.
• F7 --allow-empty sidecar status word, F12 refusing CDP combinations, F11 tagging 0.1.1 / release: owner decisions.
• F17 pyppeteer proxy-auth/UA/connect patterns: needs a live proxy/CDP run.
• Shared fetch loop, schema/sinks: out of scope. No version bump, tag or release.

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