fix(scanner): insert semicolon before identifiers starting with in

[matthew-se]

A line that starts with an identifier beginning with in followed by a digit, _ or $ (or instanceof followed by one of those) is misread as a continuation of the previous line, so no automatic semicolon is inserted:

interface A {
  a: string
  in_b: number
}

On master this parses as (MISSING "}") followed by a labeled_statement. The same happens for expression statements starting with in_b, in1, in$ or instanceof_.

scan_automatic_semicolon only treats in…/instanceof… as an identifier when the next character satisfies iswalpha. This PR widens both checks to identifier characters (iswalnum, _, $). Real in / instanceof operators across a newline still suppress the semicolon; the new corpus test covers both.

Tests

• tree-sitter test (0.24.4): 114/114 pass, including the two new cases. Both fail on master.
• tree-sitter parse --rebuild of the CI example repos (desktop, redux, vscode; 15,190 .ts/.tsx files, same excludes as CI) gives the same 51 failing files before and after.
• The repro above parses cleanly with both the typescript and tsx grammars.

tree-sitter-javascript's src/scanner.c has the same check. The same fix is in tree-sitter/tree-sitter-javascript#389.

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