Test precommit init command

Setup: create a minimal OCaml project with git
  $ mkdir test-project
  $ cd test-project
  $ git init -q
  $ echo '(lang dune 3.0)' > dune-project

Test dry-run mode shows what would be created
  $ precommit init --dry-run
  Would create $TESTCASE_ROOT/test-project/.git/hooks/
  Would create $TESTCASE_ROOT/test-project/.git/hooks/pre-commit
  Would chmod +x $TESTCASE_ROOT/test-project/.git/hooks/pre-commit
  Would create $TESTCASE_ROOT/test-project/.git/hooks/commit-msg
  Would chmod +x $TESTCASE_ROOT/test-project/.git/hooks/commit-msg
  Would create ./.ocamlformat
  ℹ Would initialise .
  ✓ Processed 1 directory

Test actual init creates the hooks
  $ precommit init
  ✓ Initialised .
  ✓ Processed 1 directory

Verify hooks exist and are executable
  $ test -x .git/hooks/pre-commit && echo "pre-commit is executable"
  pre-commit is executable
  $ test -x .git/hooks/commit-msg && echo "commit-msg is executable"
  commit-msg is executable

Verify pre-commit hook content
  $ head -2 .git/hooks/pre-commit
  #!/bin/sh
  # Auto-format OCaml files with dune before commit

Verify commit-msg hook content
  $ head -2 .git/hooks/commit-msg
  #!/bin/sh
  # Check commit message for emojis and remove AI attribution lines

Test error when not in a git repo
  $ cd /tmp
  $ mkdir no-git-$$
  $ cd no-git-$$
  $ echo '(lang dune 3.0)' > dune-project
  $ precommit init
  ✗ No git repositories found
  [1]

Test error when not in an OCaml project
  $ cd /tmp
  $ mkdir no-dune-$$
  $ cd no-dune-$$
  $ git init -q
  $ precommit init
  ℹ No OCaml projects found (use --force to install anyway)
  [1]