feat: register terminal CLI commands declaratively

[offendingcommit]

Summary

Plugin authors can now declare true terminal subcommands with
@command(type="cli") while the existing decorator remains a backward-compatible
slash command by default. This lets plugins use Hermes' native argparse
registration contract instead of treating terminal commands as in-session
command strings.

The command type is explicit in decorator metadata and registration summaries.
Slash and CLI namespaces can intentionally share a name, while duplicates
within either namespace still fail before partial registration. CLI handlers
must be synchronous, parser setup must also be synchronous, and invocation
logs do not expose parsed argument values or exception messages.

The release is versioned as 0.7.0. Existing positional
RegistrationSummary construction keeps the middleware field in its original
slot.

Validation

• make test: 80 tests passed
• Focused decorator and lifecycle suites passed
• Real Hermes PluginContext.register_cli_command contract test passed
• make build: source distribution and wheel built successfully
• git diff --check origin/main: passed

Post-Deploy Monitoring & Validation

• Watch plugin registration receipts for the expected cli_commands inventory.
• Confirm a migrated consumer can parse hermes <command> --help and dispatch
  its handler through the host CLI.
• Treat a missing command or register_cli_command signature error as rollback
  criteria.
• Roll back by pinning consumers to hermes-plugin-kit 0.6.0.
• Owner and window: plugin maintainer during the first consumer migration.

---