Windows: MSYS children glob and unescape on-file argv #1191

Found while fixing #1186 on the Windows CI job (PR #1190, run https://github.com/thekevinscott/dirsql/actions/runs/36432881839).

command::run_command spawns argv through Rust's Command::args. On Windows, Rust wraps an argument in quotes only when it contains a space or tab. An MSYS/Cygwin child (Git for Windows' sh, printf, echo, cat, ...) re-parses its command line and runs glob and brace expansion on every unquoted word, with \ as the escape character. That breaks the contract in command.rs ("no globbing", "a substituted value is always exactly one argv element") when the child is an MSYS program:

• on-file = "printf '[{}]'": printf receives [] after brace expansion, so every file yields zero rows.
• printf '[{"n":1}]' and printf ... {abspath} are mangled the same way.
• A {path} in verbatim form (\\?\C:\Users\..., which fs::canonicalize and a canonical cwd produce on Windows, and which the watcher reports) contains ?, so it is globbed, and its backslashes are eaten as escapes: the hook sees \?C:Usersrunneradmin...in_cwd.txt.

Tests red for this reason on Windows (after #1190):

• internal_tests::build_tables_from_config_creates_on_file_tables, run_on_file_parses_command_json_output, run_on_file_does_not_substitute_abspath
• async_sdk::from_config_path_loads_config_with_explicit_root
• sdk::builder_config_loads_tables_with_explicit_root, builder_appends_programmatic_tables_to_config_tables
• cli_repeatable_config_e2e::query_subcommand_accepts_repeated_config_flags, server_serves_tables_from_two_config_flags
• cli_e2e::config_elsewhere_indexes_invocation_cwd_not_config_parent
• config_root_derivation::config_without_root_indexes_process_cwd_not_config_parent (verbatim cwd)
• cli_e2e::get_events_emits_insert_event_when_file_created, cli_integration::get_events_streams_mutation_events, and probably cli_e2e::server_indexes_a_directory_moved_into_the_root (watcher paths are verbatim)

Options, not mutually exclusive:

1. On Windows, force-quote every argument (CommandExt::raw_arg with MS quoting). MSYS does not glob a quoted word, and MSVCRT children parse it the same as today. Caveat: inside quotes MSYS collapses \\ to \, which MS rules keep, so a \\?\ or UNC value still differs between the two runtimes.
2. Hand hooks a non-verbatim path (C:\... instead of \\?\C:\...). This removes the ? and the doubled backslash, and helps any Windows tool that rejects verbatim paths.
3. Declare MSYS children unsupported and rewrite the fixtures. Users on Windows would still hit this.