fix(madara): list Tangerine Archive premium chapters and fail loudly on locked bodies (replica + hardening)

[RibatTRW]

Stacked candidate fix for lnreader#2564

Base is deliberately fm/lnreader-plugins-2555-tangerine, the head branch of PR lnreader#2564 — not a default branch. Merge only after (or together with) that PR.

This is the wave-2 replica of the fm/tangerine-premium-fail-loud lane (PR #2 in this fork): same fail-loud approach, rebuilt on PR 2564's head with the hardening that lane lacked. It fixes exactly the gap PR 2564 documented: premium (coin-locked) chapters were dropped from the chapter list because their ajax rows carry href="#", and parseChapter on their real URLs returned an empty body.

What changed (plugins/multisrc/madara/{template.ts,sources.json,README.md})

New premiumChapterUrls option, off by default and enabled only for tangerinearchive (versionIncrements: 1 → plugin 2.2.1). Sources without the flag take the previous code path unchanged.

• Listing: a locked row (premium-block, href="#") gets its real chapter-<n> path reconstructed from the first number in the row's anchor text. The rule also covers the site's odd slugs: a non-ASCII token directly after the number is part of the slug (Chapter 176 🔞 → chapter-176-%f0%9f%94%9e) while a - title suffix is not (Chapter 242 - 🔞 → chapter-242), and 27.2 becomes 27-2. A row with no number is skipped rather than listed with a guessed URL.
• Duplicate-number collisions: a derived URL can collide with another row (the site has two posts titled Chapter 166 on one slug, and in principle a free row could own the same slug). Only those ambiguous rows are resolved with one extra fetch, and a row is kept only when the page's #wp-manga-current-chap[data-id] is its own data-chapter-<id>; the other row is dropped. A derived URL can therefore never be listed as a different chapter.
• parseChapter fail-loud (flag-gated): a fetched page with no chapter container (the series-page soft-404) throws Chapter content unavailable: … did not return a chapter page …; a gated page throws Premium chapter locked: costs N coins and requires a site account to unlock. (price read from the gate block, so it also covers rows listed free whose page is still gated); an empty chapter page throws a distinct "no readable text" error. Free chapters parse exactly as before.
• releaseTime is null for reconstructed rows (the site's "Unlocked in 4 weeks"/TBA is not a publication date; the template's parseData would otherwise report a past date).
• hasLocked: true exposes the existing "Hide locked chapters" switch (default off ⇒ locked rows are shown).

What was probed (all anonymous, read-only; no cookies, no login, buy endpoint never called)

• URL reconstruction, full site: 19 series from wp-manga-sitemap.xml, POST /series/<slug>/ajax/chapters/ each → 3359 rows = 2687 free + 672 premium. The rule reproduces 2669/2687 free rows' real hrefs exactly, 17 differ only by percent-encoding case (same URL), 1 is the WP duplicate-slug chapter-55_1.
• Every premium derived URL fetched (672 requests): 671/672 return HTTP 200 with the row's own data-id and the lock block; the 1 exception is the documented duplicate Chapter 166 (id 16701, resolves to sibling 16700), which this PR drops from the list. 0 soft-404s, 0 free-prose-under-premium.
• Free-chapter regression sample: 156 free pages across all series (incl. chapter-0, emoji and _1 slugs) all carry #wp-manga-current-chap + .reading-content and parse prose (median 4465 chars).
• Generated plugin probe (.scratch/probe-premium.mjs, 44/44): for 6 series the plugin's chapter count equals the live ajax list minus resolved collisions; every premium path equals the independently derived set; emoji rows 175/176 keep their emoji slug; villain Chapter 166 lists only the row that owns the slug; free garden-160/villain-144 parse 6538/7859 chars; locked garden-161/212 and the villain emoji slug throw the 10-coin message; the plain villain-176 URL (series-page soft-404) and a deliberately wrong /chapter-999/ throw the distinct "did not return a chapter page" error; hideLocked on/off gives 160/212 chapters.
• Repo checks: npm run build:multisrc, npm run build:compile, npm run check:plugin on the generated Tangerine plugin (PASS: 12 novels, 173 chapters, 14497 chars), prettier/eslint clean on the three changed files. Repo-wide eslint is unchanged from the base commit (79 problems both sides); the 10 prettier warnings are pre-existing files untouched here.
• Shared-template guard: unrelated Madara sources with the flag off — SleepyTranslations[madara] (44 chapters, 9872 chars) and Lovelyblossoms[madara] (5 chapters, 15373 chars) — both PASS.

What was NOT tested

• No entitled session: LNReader plugins cannot log in, so no locked body was read and none is served. The lock is a real server-side gate; this PR only lists the chapters honestly and names the gate.
• No purchase, no session/nonce forging, no third-party copy of the prose.
• The reader app's rendering of the thrown error (only the plugin-level error message is verified).
• The site's scheduled unlock (the one legitimate route to the prose) was not captured during this session: the soonest countdowns were 8–9 h out (it-seems-like-…/chapter-231, i-thought-…/chapter-53) and garden-of-may chapter-161 still reports "Unlocked in 1 day". A read-only flip watcher is armed to capture a flip if one lands.

Authored with AI assistance (firstmate crewmate) — reviewers should weight accordingly.