feat(compression): raise compaction trigger to 85% for gpt-5.5 on Codex OAuth (#40957)

The ChatGPT Codex OAuth backend hard-caps gpt-5.5 at a 272K context window
(verified live: a ~330K-token request to chatgpt.com/backend-api/codex/responses
is rejected with context_length_exceeded while ~250K succeeds; the same slug
exposes 1.05M on the direct OpenAI API / OpenRouter and 400K on Copilot). At the
default 50% trigger, auto-compaction fires at ~136K — half the usable window.

Raise the trigger to 85% (~231K) on this exact route only, gated by a new
compression.codex_gpt55_autoraise config flag (default true). When it fires,
emit a one-time notice (CLI inline print + gateway status_callback replay) with
the exact opt-back-out command. gpt-5.5 on any other provider keeps the user's
global threshold.

- _is_codex_gpt55() matches the 5.5 family only on provider=openai-codex
- _compression_threshold_for_model() now provider-aware + opt-out param
- config key + _config_version bump (27->28) for backfill
- docs + tests (40 cases in test_arcee_trinity_overrides.py)

hermes_cli/config.py

@@ -1139,6 +1139,16 @@ DEFAULT_CONFIG = {
                                       # Default False matches historical behavior; set to
                                       # True if you'd rather pause than silently lose
                                       # context turns when your aux model is flaky.
+        "codex_gpt55_autoraise": True,  # When True, gpt-5.5 on the ChatGPT Codex OAuth
+                                      # route raises its compaction trigger to 85% (vs the
+                                      # global `threshold` above). Codex hard-caps gpt-5.5
+                                      # at a 272K window, so the default 50% would compact
+                                      # at ~136K and waste half the usable context. Set to
+                                      # False to opt back down to the global threshold
+                                      # (e.g. 0.50) for Codex gpt-5.5 sessions. Only this
+                                      # exact route is affected — gpt-5.5 on OpenAI's
+                                      # direct API, OpenRouter, and Copilot keep the
+                                      # global threshold regardless.
     },
 
     # Anthropic prompt caching (Claude via OpenRouter or native Anthropic API).
@@ -2420,7 +2430,7 @@ DEFAULT_CONFIG = {
 
 
     # Config schema version - bump this when adding new required fields
-    "_config_version": 27,
+    "_config_version": 28,
 }
 
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