[cscheid]

Fixes #943.

What changes

A straight ' directly after a word, outside an open single quote, is now an apostrophe instead of a quote mark. Dogs' toys and cats' toys. renders as <p>Dogs’ toys and cats’ toys.</p>, matching pandoc. Also fixed: the cats'., Cats' at end of block, It's the cats' toys., and d' before a code span (one half of #221). It works at paragraph start, in list items, headings, block quotes, the first cell of a pipe table, and inside double quotes. 'Dogs' toys' still closes at the first ', and 'Hello world' still pairs.

How

The external scanner applies pandoc's notAfterString rule for ASCII words. The tree-sitter lexer cannot look behind, so the decision is made at the start of each word: the scanner reads ahead, and if the word is followed by ' plus a non-alphanumeric, it emits word' as one _pandoc_literal_str. Otherwise it returns false and the internal lexer proceeds as before.

"Outside a single quote" is a serialized single_quote_depth counter maintained in the scan wrapper (+1 on open, -1 on close, reset at line endings and block closes). valid_symbols[SINGLE_QUOTE_CLOSE] cannot serve that purpose because a closer is not accepted right after whitespace inside a quote.

One grammar change: a hidden zero-width _paragraph_start token, optional at the front of pandoc_paragraph. At a block start the scanner must also decide whether the line is a pipe-table header, and the two candidate tokens need different ends. When the first word ends in an apostrophe and the line is not a table header, the scanner emits the hint and the next call emits the word. No conflicts: were added; tree-sitter generate produced a deterministic table.

Fallout

• Regenerating the parser renumbers LR states, so _autogen-table.json and the Q-2-10 case files were rebuilt with scripts/build_error_table.ts.
• Fixtures in pampa, quarto-core, quarto and qmd-syntax-helper that used groups'-style apostrophes as their parse-error trigger now use a ' with whitespace around it, which still errors. Two LMD snapshots shifted by one column.
• docs/errors/markdown/Q-2-10.qmd, Q-2-7.qmd and the markdown migration guide are updated.
• Four claude-notes/plans/*.md files relied on an accidental pairing: a plural possessive such as packages' was read as an opening quote that a later `code`'s closed. With the possessive now an apostrophe, the ' after the code span became an unclosed opener and the strict claude-notes render failed in CI. Those apostrophes are escaped as `code`\'s, per the migration guide.

Known limits (pinned in tests)

Words starting with a digit or a non-ASCII letter (1990s', Agnès'), a ' after a closing delimiter (`a.rs`'s, still Q-2-7), and a possessive inside an emphasis inside a quote. Each keeps its previous error.

Verification

• tree-sitter test: 840/840 (10 new corpus cases in inline-quotes.txt)
• cargo xtask test: 17518 passed, 200 skipped
• clippy (-D warnings) and cargo xtask lint clean
• tree-sitter parse --time on a 300 KB document: unchanged within noise
• Windows cross-check (--target x86_64-pc-windows-msvc) could not run: the tree-sitter C build needs Windows headers. The Rust changes are tests and fixtures only.

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