test(repo): preserve carriage returns in blame fixtures

Windows CI with Git `2.56.0.windows.2` fails the historical-path regression
for its combined control-character filename under both `core.quotePath`
settings. The attributed original commit is
`e5ed22d659d5aa4ff5f7527069752d20f74fc2d9`, which a local Git reproduction
matches exactly when removing the carriage return from the original path.
Keeping that byte produces `73813b4d58d085503f9426c6e50ce5c201f715b6`.
The failure therefore comes from fixture creation losing the byte, rather
than incremental blame returning a different path from the stored tree.

Represent special paths as Git C-quoted text and feed the original tree
through `git mktree` instead of sending raw control bytes to `mktree -z`.
Git decodes the escapes while constructing the tree. This keeps carriage
returns out of the raw fixture input and retains coverage for every
control character, invalid UTF-8, literal escapes, and both quoting
settings. The parser implementation and expected results are unchanged.

The focused regression passes locally on both backends with all sixteen
subcases. Raw `git ls-tree -z HEAD~2` confirms the carriage return is
present, and the original commit retains its expected ID. ShellCheck,
`bash -n`, and `git diff --check` pass. Windows CI must verify the fixture
on its native Git/Bash combination.

Author: codex

tests/fixtures/blame-paths.sh

@@ -1,14 +1,14 @@
 #!/usr/bin/env bash
 set -eu
-# Tree entries allow historical names that cannot be checked out on every platform.
-paths=('plain.txt' ' spaced name.txt ' $'caf\303\251.txt' $'byte-\377.txt' '"literal-\303\251.txt"' 'quote"name.txt' 'back\slash.txt' $'control\a\b\t\n\v\f\r.txt')
+# C-quoted tree input preserves control bytes through Windows fixture creation.
+paths=('plain.txt' ' spaced name.txt ' '"caf\303\251.txt"' '"byte-\377.txt"' '"\"literal-\\303\\251.txt\""' '"quote\"name.txt"' '"back\\slash.txt"' '"control\a\b\t\n\v\f\r.txt"')
 for i in "${!paths[@]}"; do
     git init -q --initial-branch=main "$i"
     (
         cd "$i"
         git config core.quotePath "$1"
         blob=$(printf 'first\nmiddle\nlast\n' | git hash-object -w --stdin)
-        tree=$(printf '100644 blob %s\t%s\0' "$blob" "${paths[$i]}" | git mktree -z)
+        tree=$(printf '100644 blob %s\t%s\n' "$blob" "${paths[$i]}" | git mktree)
         original=$(git commit-tree "$tree" -m original)
         tree=$(printf '100644 blob %s\tcurrent.txt\0' "$blob" | git mktree -z)
         renamed=$(git commit-tree "$tree" -p "$original" -m rename)