fix: diff file headers and unanchored ! in diff and git

[lvolland]

hey! the two header lines of every git diff come out wrong.

await highlightText('--- a/file\n+++ b/file\n@@ -1 +1 @@\n-old\n+new', 'diff')

today --- a/file is deleted (red) and +++ b/file is insert (green), as if they were content lines. expected: both section, like the @@ line.

cause: [*-+] in the section rule is a range (U+002A–U+002B), so it holds * and + but not -. /[*-+]/.test('-') is false. and even with the class fixed nothing moves, because the rule sat last and lost the index tie to deleted/insert — the loop runs backwards and takes <=. so the class and the position both have to change.

two more in the same pass:

• /!.*/gm was unanchored, so if (a !== b) { painted !== b) { as a keyword mid-line. anchored to ^.
• git.js used expand: 'str', so every apostrophe in a commit message opened a green string. swapped for strDouble plus a prose-aware apostrophe rule.

+16 bytes in diff.js, +144 in git.js. fixture lines in test.diff and test.git.

notes

• --- <one word> now reads section instead of deleted. that hits one-word deleted sql/lua comments (-- up, -- down) — common in migrations. --- primary key (two words) is unaffected. tightening further means reasoning about the ---/+++ pair, which costs a lot more than 16 bytes.
• paths with spaces (--- a/my file.txt) are not fixed — ( \S+)?$ wants a single token. no regression, main got them wrong too, but the fix is narrower than the title suggests.
• the apostrophe rule uses a lookbehind. bash.js already has four, one of them variable-length, so no new floor.
• escapes still work: a "b\"c" d is one string, same as before. half-typed quotes stay coloured too.