fix(cli): discover pip-installed plugins via entry points in list/enable/disable

[annguyenNous]

Problem

The runtime PluginManager.discover_and_load() scans importlib.metadata entry points (hermes_agent.plugins group) to find pip-installed plugins, but the CLI commands (hermes plugins list, enable, disable) only scanned bundled and user filesystem directories.

This caused pip-installed plugins to be invisible in CLI output and impossible to enable/disable by name, even though they loaded correctly at runtime. Users installing platform adapters (discord, mattermost, etc.) via pip install hermes-agent[discord] would see No adapter available for discord in hermes gateway run but couldn't diagnose via hermes plugins list because the plugin didn't appear.

Fix

Add entry-point scanning to both _discover_all_plugins() and _plugin_exists() in hermes_cli/plugins_cmd.py:

1. _discover_all_plugins() — After scanning bundled and user directories, also check importlib.metadata.entry_points(group="hermes_agent.plugins") and add any entries not already found via filesystem scan.

2. _plugin_exists() — After checking bundled and user directories, also check entry points so hermes plugins enable <name> works for pip-installed plugins.

Both additions use the same entry-point selection pattern as PluginManager._scan_entry_points() (Python 3.12+ select() / dict fallback / list comprehension), wrapped in try/except Exception for graceful degradation.

Before vs After

Command	Before	After
hermes plugins list	Only bundled + user dir plugins	Also shows pip-installed entry-point plugins
hermes plugins enable discord	Plugin 'discord' not found	Works if pip-installed with entry point
hermes plugins info discord	Not found	Shows entry-point plugin info

Tests

No new tests added — the fix is mechanical (adds a discovery source that already exists in the runtime loader). Existing plugin CLI tests should continue to pass since the change is additive.

Fixes #34511 (related — same class of discovery gap, though that specific issue was about missing plugin.yaml manifests in the PyPI wheel).

[alt-glitch]

Duplicate of #23802 (root issue) — competing with existing PR #23814 (same fix, same scope). Closed PR #25040 was a broader attempt at the same fix. All target hermes_cli/plugins_cmd.py to add importlib.metadata.entry_points() scanning.

[teknium1]

already impl