add tests to prevent formatting regressions in ipfs ls --long output:
unit tests (core/commands/ls_test.go):
- TestFormatMode: 20 cases covering all file types (regular, dir,
symlink, pipe, socket, block/char devices) and special permission
bits (setuid, setgid, sticky with/without execute)
- TestFormatModTime: zero time, old time (year format), future time,
format length consistency
integration tests (test/cli/ls_test.go):
- explicit full output comparison with deterministic CIDs to catch
any formatting changes
- header column order verification for --long with --size=true/false
- files without preserved metadata (---------- and - placeholders)
- directory output (trailing slash, d prefix in mode)
requested in: https://github.com/ipfs/kubo/pull/11103#issuecomment-3745043561
e66fa0dbc4