feat(cli): suggest closest command or option on typos

[Chemaclass]

Why

bashdep instal printed one error line followed by 25 lines of usage. The actual mistake got buried.

What

$ bashdep instal
Error: Unknown command 'instal'. Did you mean 'install'?
Run 'bashdep --help' for usage.

$ bashdep install --dryrun
Error: Unknown option '--dryrun'. Did you mean '--dry-run'?

• Suggests the closest match within two edits. No match: just the error and the --help hint.
• --job=2 matches on the flag name, so it suggests --jobs.
• Command and flag lists move to BASHDEP_COMMANDS / BASHDEP_FLAGS, shared with completion.
• Edit distance in awk. No new runtime dependency.

Test plan

• 6 new tests (helper, command, option, =value option, no-match hint)
• Manual check on bash 3.2 and macOS awk
• make check green