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advancing from the superseded GPT-5.4/5.5 generation.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/codex-config.test.cjs

@@ -121,7 +121,7 @@ function countMatches(content, pattern) {
 }
 
 function assertNoDraftRootKeys(content) {
-  assert.ok(!content.includes('model = "gpt-5.4"'), 'does not inject draft model default');
+  assert.ok(!content.includes('model = "gpt-5.6-terra"'), 'does not inject draft model default');
   assert.ok(!content.includes('model_reasoning_effort = "high"'), 'does not inject draft reasoning default');
   assert.ok(!content.includes('disable_response_storage = true'), 'does not inject draft storage default');
 }