fix(cli): suppress spurious 'Unknown toolsets' warning for plugin toolsets validated before registration

[dcazabat]

Summary

cli.py prints a spurious Warning: Unknown toolsets: a2a (and spotify) on startup even though those plugin toolsets load and work correctly moments later.

Root cause

The HermesCLI constructor validates the enabled-toolset list via validate_toolset() before plugin toolset registration runs. Plugin toolsets like a2a / spotify are registered at plugin load time (after this constructor), so they look unknown at this early point.

The existing code already excludes MCP server names from the check for exactly this reason (MCP names resolve later during discovery). Plugin toolsets are the same class of "resolves later" name, but weren't excluded.

Fix

Mirror the MCP-name exclusion: also skip toolset names recorded in config's known_plugin_toolsets (a platform → list-of-names map written by the hermes tools save flow — see hermes_cli/tools_config.py).

mcp_names = set((CLI_CONFIG.get("mcp_servers") or {}).keys())
plugin_ts_names = {
    name
    for names in (CLI_CONFIG.get("known_plugin_toolsets") or {}).values()
    for name in (names or [])
}
invalid = [
    t
    for t in toolsets
    if not validate_toolset(t)
    and t not in mcp_names
    and t not in plugin_ts_names
]

Verification

• python3 -c "import ast; ast.parse(open('cli.py').read())" → clean.
• Confirmed a2a is present in known_plugin_toolsets on a live config, so the warning is suppressed.
• Confirmed the toolset is genuinely functional (not a masking of a real error): ✓ a2a connected in gateway.log and the a2a_* tools present in the session catalog.

Notes

• This is a source fix; it does not survive hermes update (by design — it's an upstream change).
• Related to [Bug]: hermes config logs spurious "Config ref ${env:VAR} is not set" warning for vars present in ~/.hermes/.env #89199 (same startup-ordering bug class, different symptom).

[alt-glitch]

This was generated by AI during triage.

Duplicate of #88003 for the same pre-registration plugin-toolset warning mechanism.

[teknium1]

The Unknown-toolsets startup warning now exempts plugin toolset keys via get_plugin_toolset_keys_nowait() (#116425 salvaged).

Superseded by #118841 (merge 74f726c), which credits this PR. Closing.