fix: prevent nested subparser commands from falling through to chat REPL

[gruuna-bannert]

Summary

Fixes #4184 — hermes mcp add (and other nested subparser commands) incorrectly falling through to the chat REPL instead of executing the intended subcommand.

Root Cause

On Python 3.11, argparse's nested subparser handling may leave args.func set to the parent parser's default (cmd_chat) instead of propagating the child subparser's set_defaults(func=...). The existing dispatch logic checked args.func but didn't distinguish between a genuine bare invocation and a nested-subparser bug.

Fix

When args.func == cmd_chat, check for subcommand-specific attributes (mcp_action, cron_command, gateway_command) that indicate a real subcommand was parsed. If found, dispatch to the correct handler instead of falling through to chat.

Additionally, when args.func points to a real subcommand handler (not cmd_chat), dispatch it immediately without further checks.

[alt-glitch]

Likely duplicate of #4189 — both fix nested subparser dispatch falling through to chat REPL (#4184).

[alt-glitch]

Likely duplicate of #4189 — both fix nested subparser dispatch falling through to chat REPL (#4184).

[gruuna-bannert]

@alt-glitch But #4189 is extremely bloated and includes many unrelated changes.

[teknium1]

This appears to be implemented on current main. Automated hermes-sweeper review found that the reported hermes mcp add fall-through to the chat REPL has been fixed by a later focused parser change.

Evidence:

• hermes_cli/subcommands/mcp.py:45 now declares the MCP add --command flag with dest="mcp_command", with an inline note that this avoids clobbering the top-level args.command and falling through to interactive chat.
• hermes_cli/subcommands/mcp.py:104 keeps the mcp parser routed through func=cmd_mcp.
• hermes_cli/mcp_config.py:286 reads args.mcp_command, so the user-facing --command flag still works.
• tests/hermes_cli/test_mcp_add_command_dest.py:49 covers hermes mcp add foo --url ... and asserts args.command == "mcp" instead of None.
• Fix commit: 4f364c4e99d46a0c50d3ea1d5ad179f54348f9f7 (fix(mcp): give 'mcp add --command' a distinct argparse dest), contained in v2026.5.7 and later tags.

Thanks for the focused PR and for the follow-up discussion about #4189 being broader than necessary; the narrower behavior this PR targeted is now covered on main.