fix(cli): validate plugin toolsets against persisted plugin-key cache

[iskandarsulaili]

What

HermesCLI._init_toolsets validated toolset names only against the live tool registry, but plugins register their toolsets in a background discovery thread that may not have joined by the time init runs. Every enabled plugin toolset (e.g. agents, lsp, vault, searxng, orchestra) was therefore falsely printed as:

Warning: Unknown toolsets: agents, anchored, cloakbrowser, ...

while the tools themselves still loaded fine — pure warning noise on every CLI start.

Fix

Also accept the persisted plugin-toolset-key cache (get_plugin_toolset_keys_nowait()) when validating, matching the exact pattern already used by hermes_cli/oneshot.py (_validate_explicit_toolsets) and tui_gateway/server.py (_resolve_explicit_toolsets). Import is tolerant; on any exception the set is empty and behavior falls back to today's code.

Why this is safe

• get_plugin_toolset_keys_nowait() returns the persisted cache while background discovery is in flight (never blocks), and self-heals on the next scan.
• Only silences the false "unknown" notice; does not change which tools load.
• Mirrors the two existing validated-code sites for the identical problem.
• Tests for validate_toolset() are unchanged (static + plugin-registered + MCP names still validate as before).

Reproduction

$ hermes
Warning: Unknown toolsets: agents, anchored, cloakbrowser, codegraph, codegraph-context, cross-memory, dsh, effect, google_meet, graphify, lsp, memory-tdai, moa-trigger, orchestra, searxng, semble, vault

[alt-glitch]

This was generated by AI during triage.

Duplicate of #89345 -- that open PR applies the same get_plugin_toolset_keys_nowait() check in cli.py._init_toolsets (plus the subagent-lifecycle path and tests). Related competing approaches: #91761, #29774, #25714.

[iskandarsulaili]

Closing as a duplicate. Superseded by #89345 (adamkrawczyk), which applies the same get_plugin_toolset_keys_nowait() fix in cli.py plus the subagent_lifecycle.py validation path and regression tests. No further action needed on this PR.