[ogffx]

Fixes #188.

The regular expressions added in #160 to avoid backtracking match a single backslash (\\+? is lazy), so only one backslash of a run before " or at the end of an argument gets doubled. Arguments passed to a .cmd/.bat can then split or swallow their neighbours:

spawn.sync('node_modules/.bin/echo-cmd-shim', ['x\\\\" --foo \\\\', 'bar'])
// argv received with 7.0.6:   ["x\\\\", "--foo", "\\\"", "bar"]
// argv received with this PR: ["x\\\\\" --foo \\\\", "bar"]

Making the quantifier greedy fixes the output but brings back the quadratic case from #160 (~30 s for 160 KB of backslashes on my machine). This PR replaces both expressions with a single pass that matches each run of backslashes as a whole, so it stays linear (~1 ms for the same input).

Testing:

• Output is identical to 7.0.3 on 300,000 random arguments (backslashes, quotes and meta chars, with and without doubleEscapeMetaChars).
• New lib/util/escape.test.js (backslash runs before " and at the end, a linear-time check) and a Windows end-to-end test through the .cmd shim. 6 tests fail without the change; npm test passes with it (92 tests, Windows 11, Node 24), and lint passes.

This change was prepared with AI assistance. I reviewed it and ran the checks above myself.

🤖 Generated with Claude Code