fix(model-switch): separate picker rows for same-endpoint proxies with distinct names (salvages #67747)

[teknium1]

Summary

custom_providers: entries sharing one endpoint but carrying distinct display names (aggregating proxies — LiteLLM fronting cerebras/groq/perplexity at a single URL) now get separate picker rows instead of silently merging into one. Salvages #67747 (@craigdfrench) onto current main with authorship preserved.

Changes

• hermes_cli/model_switch.py: section-4 group key gains a display-name-prefix dimension — (api_url, credential_identity, api_mode, headers_identity, display_prefix). Extends current main's tuple (per the sweeper's prescription on fix: group custom_providers by (endpoint, name) to support proxy setups #21544), so the credential/mode/headers safeguards from aa283d1e4/ed4123792 are intact. The em-dash suffix fold ("Ollama — A" + "Ollama — B" → one "Ollama" row) is preserved because those entries share the prefix.
• Tests: test_shared_url_different_display_names_are_separate_rows + test_shared_url_per_model_suffix_still_collapses (cherry-picked). Follow-up ours: dropped the PR's duplicate fetch_api_models mocks on 3 tests already hermetic via test(model): isolate custom-provider grouping tests from live discovery #62421's probe_custom_providers=False (merged as test(model): isolate custom-provider grouping tests from live discovery (salvages #62421) #67921).

Credit also to @chiyema — #21544 proposed the name-discriminator concept first (May 7); its implementation predated the credential/mode/headers hardening and would have regressed it.

Validation

Check	Result
test_model_switch_custom_providers.py + test_provider_section3_grouping.py + test_list_picker_providers.py	68/68 pass
E2E, real imports: mixed config with section-3 providers: (Palantir 2-entry fold) + section-4 proxy entries	section 3 still folds by endpoint identity ("Palantir Claude", 2 models); section 4 yields separate Cerebras/Groq rows — no interference with #67908

Infographic

[alt-glitch]

This was generated by AI during triage.

Maintainer salvage of #67747 and related to #21544. It carries the same display-prefix idea but preserves the newer credential/mode/header grouping contract, so maintainers should choose the current-main-aware implementation.