v0.1.0 — comments, video metadata and search

First release. Three modes, three browser engines, and a Scraper API
client, reading YouTube through the endpoint its own front end calls.

Added

• --mode comments — a video's comment threads and, with --replies,
  their replies. 20 top-level comments per page, 10 replies per page.
  --sort top|newest selects between the site's two orderings.
• --mode video — one video's metadata, from two calls: next for
  the rendered figures and player for the exact upload date, the
  duration in seconds, the category and the keyword list. The only mode
  that can use --concurrency, because a video has its own address and a
  comment page does not.
• --mode search — a query to videos, to feed --mode comments.
• playwright_scraper.py, puppeteer_scraper.py and
  selenium_scraper.py: one file with three driver layers, so the shared
  half cannot drift. Verified live on 2026-09-21 — the same video and
  ordering through all three gave 40 rows each, 40 ids in common and zero
  disagreeing columns.
• scraper_api_client.py for --mode video only. It cannot read comments
  on this site, and the measurement is in its docstring and the README.
• diff_runs.py, which refuses to compare two runs whose ordering differs
  — on this site the ordering decides which comments a capped run holds,
  not merely their order.
• An offline suite of 639 checks that passes with no engine library
  installed, and make_fixtures.py, which proves every trimmed fixture
  parses identically to its untrimmed original before writing it.

Measured, and worth knowing before choosing this

• The comment endpoint is not gated. 2026-09-21, from a bare
  datacentre address in Finland with no key, no proxy, no cookies and no
  account: 60 consecutive pages, 1,200 comments, zero refusals, ~0.25 s
  per page.
• YouTube publishes no exact like count for a comment, and no absolute
  timestamp, to any client — checked under WEB, MWEB and TVHTML5 over 70
  comments in four captures. So like_count is a magnitude beside
  like_count_text, and published_at_approx is derived, labelled with
  published_at_precision, and null in any locale this parser does not
  read. A video row has both exactly, which is why --mode video exists.
• The site serves two payload shapes. The WEB client returns the
  entity form, where the comment text lives in
  frameworkUpdates.entityBatchUpdate.mutations and the renderer tree
  holds only keys; the MWEB client still returns the legacy
  commentRenderer form. Both are parsed, both are pinned to a real
  capture, and data_source says which was read.
• The Scraper API cannot return comments here, because YouTube renders
  none into its HTML and fetches them over a POST the service does not
  make. A waitFor on the comment section times out (HTTP 408); a
  networkidle wait returns 1.39 MB with zero comments. Control: a
  deliberately wrong key answered 401 in 0.1 s against the real key's 200
  in 6.7 s.
• The Scraping Browser path is live-verified, on Playwright and
  pyppeteer (Selenium cannot reach an authenticated CDP endpoint and
  refuses it by name). A US profile returned comments, video metadata and
  search normally on 2026-09-21. Its WebSocket upgrade answered HTTP 500
  on one of three attempts seconds apart, so both engines now retry it —
  and its auto-solve extension injects cf-turnstile and fifteen other
  captcha markers into pages the site served normally, which is why none
  of them is in this repo's block-marker set and why a fixture cut from
  such a page is now in the suite.
• No challenge has ever been rendered to this scraper, and the served
  page's own greps mislead: recaptcha appears once, in a CSS rule that
  hides a badge, and botguard thirteen times, all of them configuration
  flags. The site's actual defence is its own attestation (bgChallenge),
  which is not a solvable widget. The captcha machinery is carried as
  readiness and says so.

Notes on what is not verbatim

fixtures_generated.json, sample_output.json and sample_output.csv are
cut from real runs and then anonymised: a commenter's display name,
channel id, avatar, comment id and own words are replaced with
placeholders. Everything the site generates around them — counts,
timestamps, badges, the video and its publisher — is untouched. A comment
is a person's writing, and republishing it is a separate act from YouTube
showing it on its own page.