refactor(gitcheck): clarify RE_CMD_SEP regex and document alternation order

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: frits-v

CLAUDE.md

@@ -177,7 +177,7 @@ All shell scripts follow the [Google Shell Style Guide](https://google.github.io
 
 ## Testing
 
-219 tests (166 unit + 5 doc + 13 integration + 10 proptest + 25 memory) plus 4 fuzz targets.
+258 tests (204 hooks unit + 5 claude_md + 13 integration + 10 proptest + 22 memory unit + 4 memory integration) plus 4 fuzz targets.
 Run with `make test` or `cargo test`.
 
 Test patterns:

hooks/src/gitcheck.rs

@@ -61,7 +61,8 @@ static RE_GIT_C: LazyLock<Regex> =
 static RE_CD_PATH: LazyLock<Regex> =
     LazyLock::new(|| Regex::new(r#"\bcd\s+("[^"]+"|'[^']+'|\S+)"#).unwrap());
 // Bare mutating git detection (segment splitting + subcommand extraction)
-static RE_CMD_SEP: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"&&|\|\||[;&|]").unwrap());
+// Matches &&, ||, then single ;, |, or & (background). || before [;|&] so double-pipe isn't split.
+static RE_CMD_SEP: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"&&|\|\||[;|&]").unwrap());
 static RE_GIT_WORD_BOUNDARY: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"\bgit\b").unwrap());
 
 /// Mutating git subcommands that must target a worktree, not CWD.