feat(codex): advance Codex/OpenAI model defaults to GPT-5.6 (Sol/Terra/Luna)

Update runtimeTierDefaults.codex and providerPresets.openai in
model-catalog.json to the GPT-5.6 family (gpt-5.6-sol/terra/luna),
advancing from the superseded GPT-5.4/5.5 generation.

Model IDs verified against OpenAI developer API docs:
- gpt-5.6-sol: flagship, /, reasoning xhigh
- gpt-5.6-terra: balanced, .50/, reasoning medium
- gpt-5.6-luna: fast/cheap, /, reasoning medium

Tier mapping is 1:1 (Sol↔flagship, Terra↔balanced, Luna↔fast),
so profile semantics are unchanged — only the underlying IDs advance.

Updates: catalog JSON, test assertions (catalog defaults), docs
(CONFIGURATION.md + zh-CN/pt-BR translations, workflow settings),
and changeset.

Closes #2122

tests/workflow-size-baseline.json

@@ -68,9 +68,9 @@
   "scan.md": 7732,
   "secure-phase.md": 13520,
   "session-report.md": 4044,
-  "settings-advanced.md": 39718,
+  "settings-advanced.md": 39728,
   "settings-integrations.md": 15892,
-  "settings.md": 33457,
+  "settings.md": 33467,
   "ship.md": 24691,
   "sketch-wrap-up.md": 14267,
   "sketch.md": 20004,