fix: prevent duplicate provider entries in /model picker (Section 3 dedup)

[ShuaiHui]

Summary

Fixes duplicate provider entries in the /model picker when a provider exists in both the built-in catalog and the user's config.yaml providers: section.

Problem

list_authenticated_providers() builds the provider list in 4 sections. Section 3 (user-defined providers from config.yaml providers:) is the only section that doesn't check seen_slugs before adding entries. This causes every provider defined in both the built-in catalog and user config to appear twice:

Built-in entry (Section 2)	Duplicate (Section 3)
"Nous Portal (27)"	"nous (0)"
"GitHub Copilot (14)"	"copilot (0)"
"DeepSeek (2)"	"deepseek (0)"
"MiniMax (7)"	"minimax (0)"

The Section 3 entries always show 0 models because they use default_model (which is typically empty for built-in provider overrides) instead of the curated model list.

Root Cause

In hermes_cli/model_switch.py, list_authenticated_providers():

• Section 1 (PROVIDER_TO_MODELS_DEV): ✅ checks seen_slugs, adds to seen_slugs
• Section 2 (HERMES_OVERLAYS): ✅ checks seen_slugs, adds to seen_slugs
• Section 3 (user_providers): ❌ no dedup at all
• Section 4 (custom_providers): ✅ checks seen_slugs, adds to seen_slugs

Fix

Add seen_slugs check and tracking in Section 3, matching the pattern used by all other sections:

# Skip if this provider was already added by Sections 1/2
if ep_name in seen_slugs:
    continue
# ... existing logic ...
seen_slugs.add(ep_name)

Verification

from hermes_cli.model_switch import list_authenticated_providers

providers = list_authenticated_providers(
    current_provider="nous",
    user_providers={"nous": {}, "minimax-cn": {}, "copilot": {}, "deepseek": {}, "minimax": {}},
    max_models=50,
)

slugs = [p["slug"] for p in providers]
# Before fix: nous appears twice, copilot appears twice, etc.
# After fix: each provider appears exactly once
assert len(slugs) == len(set(slugs))

Related

• Fixes Bug: /model provider picker shows duplicate entries when provider exists in both built-in catalog and config.yaml #7524
• Related: Bug: /model gateway command omits Hermes-overlay providers (e.g. openai-codex) #5223 (overlay providers omitted — fixed by fix: resolve overlay provider slug mismatch in /model picker #7373)
• Related: fix: resolve overlay provider slug mismatch in /model picker #7373 (overlay slug mismatch — fixed Section 2 but not Section 3)
• Related: provider config split: /model picker and runtime named custom providers use different config sources #7054 (broader config split architecture issue)