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advancing from the superseded GPT-5.4/5.5 generation.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/install-runtime-artifacts.test.cjs

@@ -3448,7 +3448,7 @@ describe('#443 Config-driven: effort.agent_overrides drives install-time effort'
     const tomlContent = fs.readFileSync(
       path.join(codexHome, 'agents', 'gsd-planner.toml'), 'utf8'
     );
-    assert.match(tomlContent, /^model\s*=\s*"gpt-5.5"$/m,
+    assert.match(tomlContent, /^model\s*=\s*"gpt-5.6-sol"$/m,
       `gsd-planner.toml should pin Codex model when runtime:"codex" is configured\nActual:\n${tomlContent.slice(0, 500)}`);
     assert.match(tomlContent, /^model_reasoning_effort\s*=\s*"low"$/m,
       `gsd-planner.toml should have model_reasoning_effort = "low" from config override\nActual:\n${tomlContent.slice(0, 500)}`);
@@ -3474,7 +3474,7 @@ describe('#443 Config-driven: effort.agent_overrides drives install-time effort'
     const tomlContent = fs.readFileSync(
       path.join(codexHome, 'agents', 'gsd-planner.toml'), 'utf8'
     );
-    assert.match(tomlContent, /^model\s*=\s*"gpt-5.5"$/m,
+    assert.match(tomlContent, /^model\s*=\s*"gpt-5.6-sol"$/m,
       `gsd-planner.toml should pin Codex model when runtime:"codex" is configured\nActual:\n${tomlContent.slice(0, 500)}`);
     // Codex does not support 'max' → clamped to 'xhigh'
     assert.match(tomlContent, /^model_reasoning_effort\s*=\s*"xhigh"$/m,
@@ -3559,7 +3559,7 @@ describe('#443 resolveInstallTimeEffort: invalid tokens fall through to valid ef
     const tomlContent = fs.readFileSync(
       path.join(codexHome, 'agents', 'gsd-planner.toml'), 'utf8'
     );
-    assert.match(tomlContent, /^model\s*=\s*"gpt-5.5"$/m,
+    assert.match(tomlContent, /^model\s*=\s*"gpt-5.6-sol"$/m,
       `gsd-planner.toml should pin Codex model when runtime:"codex" is configured\nActual:\n${tomlContent.slice(0, 500)}`);
     const match = tomlContent.match(/^model_reasoning_effort\s*=\s*"([^"]+)"/m);
     assert.ok(match, `model_reasoning_effort must be present in .toml\nActual:\n${tomlContent.slice(0, 500)}`);