feat(cli): add list_picker_providers for credential-filtered picker

[Tkander1715]

What

Adds list_picker_providers() — a thin wrapper around list_authenticated_providers() that post-processes the result so the interactive /model picker (Telegram, Discord) only surfaces models the user can actually call. _handle_model_command() in gateway/run.py switches to the new helper for the interactive picker payload only.

Why

Two failure modes today when a user opens /model:

1. Stale OpenRouter IDs — OPENROUTER_MODELS is a static snapshot. When OpenRouter drops or renames a model upstream between Hermes releases, the picker still offers it; tapping it fails at call time.
2. Empty provider rows — a credential-pool slug can exist with no actual key material behind it (e.g. leftover from a prior provider that's been env-wiped). The picker shows the row, the user taps, nothing happens.

The filter fixes both without changing list_authenticated_providers(), which is also consumed by the CLI text fallback where the unfiltered view is arguably still the right default.

How it works

• For the openrouter row, models are replaced with the output of fetch_openrouter_models(), which already cross-checks the curated snapshot against the live OpenRouter catalog.
• Rows with an empty models list are dropped, except custom endpoints (is_user_defined=True with an api_url) where the user may enter model IDs manually.
• All other fields pass through unchanged.

Typed /model <name> and the text fallback list stay on list_authenticated_providers(), so nothing is hidden from power users or platforms without an interactive picker.

How to test

pytest tests/hermes_cli/test_list_picker_providers.py -v

Nine focused unit tests covering:

• OpenRouter models replaced with live catalog
• Fallback to base models when the live fetch raises
• Empty live catalog drops the OpenRouter row
• Non-OpenRouter rows passed through unchanged
• Empty models row dropped
• Custom endpoint with api_url kept when models empty
• User-defined row without api_url and empty models dropped
• max_models caps OpenRouter live output
• All kwargs forwarded to the base function

Manual test: open /model in Telegram with a setup that exercises each branch — OpenRouter + a direct provider + a user-defined custom endpoint.

Platforms tested

• macOS (Darwin 25.4.0, Python 3.11)

Notes

• No config/schema changes, no new dependencies, no migration path.
• The branch is based on an older main (fork was behind by ~800 commits and syncing required a workflow OAuth scope I didn't have). The three files touched cherry-picked onto current main cleanly in my local worktree — happy to rebase on request.

[alt-glitch]

Related to #12655 (picker_providers config filter) and #3710 (interactive model picker feature).