fix(plugins): show entry-point plugins in 'hermes plugins list'

[MrGDCrazy]

Summary

hermes plugins list was missing pip-installed plugins that register via the hermes_agent.plugins entry-point group. The plugins were loaded and active (PluginManager.discover_and_load scans entry points correctly) — they just didn't appear in the list output because the display path (_discover_all_plugins in plugins_cmd.py) only scanned directories.

Root cause

Two separate discovery paths diverged:

Path	File	Scans dirs	Scans entry points
Loader	plugins.py PluginManager._scan_entry_points	✅	✅
Display	plugins_cmd.py _discover_all_plugins	✅	❌

Fix

Added _discover_entry_point_plugins() in plugins_cmd.py mirroring PluginManager._scan_entry_points, and appended its results to the seen dict after directory scanning (entry-points don't override directory plugins on key collision).

Testing

• 27/27 plugin tests pass (4 original list tests + 2 new entry-point tests + 21 category discovery tests)
• 3 existing category discovery tests patched to mock _discover_entry_point_plugins (return []) so they stay isolated from real pip-installed plugins
• 2 new tests: test_discover_entry_point_plugins_returns_tuples, test_discover_all_plugins_includes_entry_points
• Pre-existing async test failures in test_plugin_runtime_disable_gate.py are unrelated (missing pytest-asyncio)

Verification

Before:

$ hermes plugins list --plain | grep rtk
(no output)

After:

$ hermes plugins list --plain | grep rtk
enabled      entrypoint 1.2.3    rtk-rewrite

Fixes #58644

[alt-glitch]

This was generated by AI during triage.

Duplicate of #23814 — same fix: mirror PluginManager._scan_entry_points into the hermes plugins list display path (_discover_all_plugins in plugins_cmd.py) so pip-installed entry-point plugins are surfaced. #23814 is the earliest open canonical PR of this saturated cluster (closed #34533/#40346, open #40623/#54150). Fixes the same issue tracked by #58644/#23802.