Keep long-form fixtures to known reading

tests/fixtures/KNOWN_READING.md

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+# Known-reading fixture rule
+
+Long-form reading fixtures are for judging IB against material the maintainer actually knows. Public-domain availability is not, by itself, a reason to add a work.
+
+A work should be used as a judgment fixture only when it has been read well enough, and recently enough, that browser behavior can be meaningfully assessed against memory of the text and its structure.
+
+Current known-reading cases include:
+
+- *Njál's Saga*;
+- the Sherlock Holmes stories, with enough familiarity to use *The Adventures of Sherlock Holmes* as a whole-collection fixture;
+- Carlo Levi's *Christ Stopped at Eboli*;
+- several works by Leonardo Sciascia;
+- Eiji Yoshikawa's *Musashi*;
+- Ha Jin's *A Free Life*.
+
+Only sources that may legally be referenced as repository fixtures belong in `public-domain-reading.tsv`. Copyrighted known-reading cases can be exercised through user-owned or local representations without committing their text.
+
+Do not add an unread classic merely to obtain a convenient structural example. Also do not use a work as a primary judgment fixture when it was read so long ago that detailed comparison is no longer reliable. *Moby-Dick* falls in that latter category for current testing; *War and Peace* is not a known-reading case.

tests/fixtures/public-domain-reading.tsv

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 slug	title	author	kind	first_published	source	source_id	source_page	plain_text	reader_role	rights
 njals-saga	The Story of Burnt Njal	Anonymous; translated by George Webbe Dasent	saga	13th century	Project Gutenberg	17919	https://www.gutenberg.org/ebooks/17919	https://www.gutenberg.org/ebooks/17919.txt.utf-8	long episodic narrative with named episodes genealogy law and non-novel structure	public-domain-us
-sherlock-adventures	The Adventures of Sherlock Holmes	Arthur Conan Doyle	story_collection	1892	Project Gutenberg	1661	https://www.gutenberg.org/ebooks/1661	https://www.gutenberg.org/ebooks/1661.txt.utf-8	independent story boundaries and non-linear entry	public-domain-us
-sherlock-hound	The Hound of the Baskervilles	Arthur Conan Doyle	novel	1902	Project Gutenberg	2852	https://www.gutenberg.org/ebooks/2852	https://www.gutenberg.org/ebooks/2852.txt.utf-8	ordinary chaptered detective novel	public-domain-us
-frankenstein	Frankenstein; or, The Modern Prometheus	Mary Wollstonecraft Shelley	novel	1818	Project Gutenberg	84	https://www.gutenberg.org/ebooks/84	https://www.gutenberg.org/ebooks/84.txt.utf-8	letters and nested narration	public-domain-us
-dracula	Dracula	Bram Stoker	novel	1897	Project Gutenberg	345	https://www.gutenberg.org/ebooks/345	https://www.gutenberg.org/ebooks/345.txt.utf-8	dated journals letters and inserted documents	public-domain-us
-moby-dick	Moby-Dick; or, The Whale	Herman Melville	novel	1851	Project Gutenberg	2701	https://www.gutenberg.org/ebooks/2701	https://www.gutenberg.org/ebooks/2701.txt.utf-8	many short and long chapters plus front matter	public-domain-us
-war-and-peace	War and Peace	Leo Tolstoy; translated by Louise and Aylmer Maude	novel	1869	Project Gutenberg	2600	https://www.gutenberg.org/ebooks/2600	https://www.gutenberg.org/ebooks/2600.txt.utf-8	very large multi-book stress text	public-domain-us
-pride-and-prejudice	Pride and Prejudice	Jane Austen	novel	1813	Project Gutenberg	1342	https://www.gutenberg.org/ebooks/1342	https://www.gutenberg.org/ebooks/1342.txt.utf-8	conventional chaptered prose baseline	public-domain-us
+sherlock-adventures	The Adventures of Sherlock Holmes	Arthur Conan Doyle	story_collection	1892	Project Gutenberg	1661	https://www.gutenberg.org/ebooks/1661	https://www.gutenberg.org/ebooks/1661.txt.utf-8	familiar Holmes collection with independent story boundaries and non-linear entry	public-domain-us