fix(auxiliary): resolve named custom providers and 'main' alias in auxiliary routing (#5978)

* fix(telegram): replace substring caption check with exact line-by-line match

Captions in photo bursts and media group albums were silently dropped when
a shorter caption happened to be a substring of an existing one (e.g.
"Meeting" lost inside "Meeting agenda"). Extract a shared _merge_caption
static helper that splits on "\n\n" and uses exact match with whitespace
normalisation, then use it in both _enqueue_photo_event and
_queue_media_group_event.

Adds 13 unit tests covering the fixed bug scenarios.

Cherry-picked from PR #2671 by Dilee.

* fix: extend caption substring fix to all platforms

Move _merge_caption helper from TelegramAdapter to BasePlatformAdapter
so all adapters inherit it. Fix the same substring-containment bug in:
- gateway/platforms/base.py (photo burst merging)
- gateway/run.py (priority photo follow-up merging)
- gateway/platforms/feishu.py (media batch merging)

The original fix only covered telegram.py. The same bug existed in base.py
and run.py (pure substring check) and feishu.py (list membership without
whitespace normalization).

* fix(auxiliary): resolve named custom providers and 'main' alias in auxiliary routing

Two bugs caused auxiliary tasks (vision, compression, etc.) to fail when
using named custom providers defined in config.yaml:

1. 'provider: main' was hardcoded to 'custom', which only checks legacy
   OPENAI_BASE_URL env vars. Now reads _read_main_provider() to resolve
   to the actual provider (e.g., 'custom:beans', 'openrouter', 'deepseek').

2. Named custom provider names (e.g., 'beans') fell through to
   PROVIDER_REGISTRY which doesn't know about config.yaml entries.
   Now checks _get_named_custom_provider() before the registry fallback.

Fixes both resolve_provider_client() and _normalize_vision_provider()
so the fix covers all auxiliary tasks (vision, compression, web_extract,
session_search, etc.).

Adds 13 unit tests. Reported by Laura via Discord.

---------

Co-authored-by: Dilee <uzmpsk.dilekakbas@gmail.com>

agent/auxiliary_client.py

@@ -1142,7 +1142,13 @@ def resolve_provider_client(
     if provider == "codex":
         provider = "openai-codex"
     if provider == "main":
-        provider = "custom"
+        # Resolve to the user's actual main provider so named custom providers
+        # and non-aggregator providers (DeepSeek, Alibaba, etc.) work correctly.
+        main_prov = _read_main_provider()
+        if main_prov and main_prov not in ("auto", "main", ""):
+            provider = main_prov
+        else:
+            provider = "custom"
 
     # ── Auto: try all providers in priority order ────────────────────
     if provider == "auto":
@@ -1238,6 +1244,28 @@ def resolve_provider_client(
                        "but no endpoint credentials found")
         return None, None
 
+    # ── Named custom providers (config.yaml custom_providers list) ───
+    try:
+        from hermes_cli.runtime_provider import _get_named_custom_provider
+        custom_entry = _get_named_custom_provider(provider)
+        if custom_entry:
+            custom_base = custom_entry.get("base_url", "").strip()
+            custom_key = custom_entry.get("api_key", "").strip() or "no-key-required"
+            if custom_base:
+                final_model = model or _read_main_model() or "gpt-4o-mini"
+                client = OpenAI(api_key=custom_key, base_url=custom_base)
+                logger.debug(
+                    "resolve_provider_client: named custom provider %r (%s)",
+                    provider, final_model)
+                return (_to_async_client(client, final_model) if async_mode
+                        else (client, final_model))
+            logger.warning(
+                "resolve_provider_client: named custom provider %r has no base_url",
+                provider)
+            return None, None
+    except ImportError:
+        pass
+
     # ── API-key providers from PROVIDER_REGISTRY ─────────────────────
     try:
         from hermes_cli.auth import PROVIDER_REGISTRY, resolve_api_key_provider_credentials
@@ -1358,6 +1386,11 @@ def _normalize_vision_provider(provider: Optional[str]) -> str:
     if provider == "codex":
         return "openai-codex"
     if provider == "main":
+        # Resolve to actual main provider — named custom providers and
+        # non-aggregator providers need to pass through as their real name.
+        main_prov = _read_main_provider()
+        if main_prov and main_prov not in ("auto", "main", ""):
+            return main_prov
         return "custom"
     return provider