v1.2.0

Added

• Subcommand support on ArgParser. ArgParser subcommand(String name) registers a
  named subcommand and returns its own independent ArgParser, configured with the same
  addFlag/addOption builder methods as the top-level parser.
• ArgParser.parse(String[]) now dispatches on the first argument when one or more
  subcommands are registered: a match parses the remaining arguments against that
  subcommand's own parser; an unrecognized name throws ArgParseException.
• ParsedArgs.subcommandName() / ParsedArgs.subcommand() expose the invoked subcommand's
  name and its own, independently-parsed result.
• A parser with no registered subcommands is completely unaffected — fully backwards
  compatible with v1.1.0.

Tested

• Two subcommands registering an overlapping option name (--port) with different shapes
  (a value-taking option on one, a boolean flag on the other) parse independently, proving
  no cross-contamination between subcommand registrations.
• Parsing an unrecognized subcommand name throws ArgParseException naming the bad token.
• All existing tests continue to pass unmodified.

Docs

• New ## Subcommands section in the README with a runnable deploy/rollback example.
• A second worked example added to ## Usage.

See CHANGELOG.md for full details.