fix(cache): drop ttl=1h on Portal Qwen — Alibaba upstream is 5m-only (#24702)

PR #24151 routed Portal Qwen (qwen3.6-plus) through the prefix_and_2
long-lived cache layout, attaching {"type":"ephemeral","ttl":"1h"}
markers to the tools[-1] entry and the stable system-prefix block.
That layout works for Portal Claude because Anthropic / OpenRouter on
Anthropic routes honour 1h TTL — but Portal Qwen ultimately proxies to
Alibaba DashScope, which documents a single "ephemeral" TTL of 5
minutes on its Context Cache. The ttl="1h" qualifier is silently
dropped upstream, so the two highest-value breakpoints (tools array +
system prefix) never land. Only the rolling-window 5m markers on the
last 2 messages cache, which matches the observed ~25% read rate.

Fix: keep Portal Qwen on cache_control via _anthropic_prompt_cache_policy
returning (True, False), but drop it from _supports_long_lived_anthropic_cache
so it rides the standard system_and_3 5m layout (system + last 3 messages,
all at 5m). Same 4 breakpoints, all in a TTL the upstream actually honours.

Refs: https://www.alibabacloud.com/help/en/model-studio/context-cache
      https://openrouter.ai/docs/features/prompt-caching (Alibaba Qwen
      section: "TTL: 5 minutes")

- _supports_long_lived_anthropic_cache: Portal scope narrowed back to Claude
- tests: flip the two qwen long-lived expectations to False, retitle
  non_claude_non_qwen_rejected -> non_claude_rejected

run_agent.py

@@ -3619,12 +3619,19 @@ class AIAgent:
         is_claude = "claude" in model_lower
         is_nous_portal = "nousresearch" in eff_base_url.lower()
 
-        # Nous Portal: Claude AND Qwen both get long-lived caching.
-        # Portal proxies to OpenRouter with identical cache_control
-        # semantics; any model on Portal that accepts envelope-layout
-        # markers via _anthropic_prompt_cache_policy also benefits from
-        # the documented 1h cross-session TTL.
-        if is_nous_portal and (is_claude or "qwen" in model_lower):
+        # Nous Portal Claude rides the 1h prefix_and_2 layout (Portal
+        # proxies to OpenRouter, which honours ttl=1h on Anthropic
+        # routes).  Qwen does NOT — Alibaba DashScope (the upstream for
+        # all Qwen routes, including Portal -> OpenRouter -> Alibaba)
+        # documents a single ``ephemeral`` TTL of 5 minutes; ttl="1h"
+        # on Qwen markers is silently ignored upstream, so the
+        # high-value tools[-1] + system-prefix breakpoints never land
+        # and only the 5m rolling-window markers on the last 2 messages
+        # get cached.  Portal Qwen still gets cache_control via
+        # _anthropic_prompt_cache_policy returning (True, False) — it
+        # just rides the standard system_and_3 5m layout instead of the
+        # mismatched prefix_and_2 1h layout.
+        if is_nous_portal and is_claude:
             return True
 
         if not is_claude: