fix: show custom models in combo picker for providers with short aliases

[zerray]

Summary

When users add a custom model to an API-key provider with a short alias (e.g. DeepSeek → ds) from the dashboard, the model saves and tests successfully but never appears in the combo model picker.

Root cause

Two independent provider-alias mappings diverge for a subset of API-key providers:

• Write path — src/app/(dashboard)/dashboard/providers/[id]/page.js uses getProviderAlias(providerId) (from src/shared/constants/providers.js, reading AI_PROVIDERS[id].alias). For DeepSeek this returns "ds", so the alias is stored as modelAliases["foo"] = "ds/foo".
• Read path — src/shared/components/ModelSelectModal.js filters custom models with PROVIDER_ID_TO_ALIAS[providerId] (from open-sse/config/providerModels.js, only covers OAuth short aliases). For DeepSeek this returns "deepseek", so "ds/foo".startsWith("deepseek/") is false and the model is filtered out.

Routing itself is unaffected — open-sse/services/model.js ALIAS_TO_PROVIDER_ID explicitly accepts both ds and deepseek → deepseek, which is why Test succeeds and real requests route correctly. The bug is display-only in the combo picker.

Affected providers

Any provider where AI_PROVIDERS[id].alias !== id and the id is not in OAUTH_ALIASES:

deepseek (ds), perplexity (pplx), hyperbolic (hyp), blackbox (bb), chutes (ch), huggingface (hf), deepgram (dg), assemblyai (aai), nanobanana (nb), elevenlabs (el), brave-search (brave), vertex-partner (vxp), opencode-go (ocg), volcengine-ark (ark).

Fix

Align the combo picker with the write path by using getProviderAlias(providerId). Since routing accepts both prefixes, no data migration is needed — existing orphaned ds/… entries become visible immediately.

Providers where getProviderAlias(id) === PROVIDER_ID_TO_ALIAS[id] (most of them) are unaffected.

Test plan

• Dashboard → API Key Providers → DeepSeek → Add Custom Model (e.g. deepseek-chat-custom) → Save
• Combo form → Select Model → DeepSeek group now lists the custom model with a custom badge
• Existing combos referencing built-in DeepSeek models still render and route correctly
• Non-short-alias providers (OpenAI, Anthropic, Claude, etc.) behave unchanged

🤖 Generated with Claude Code