fix(kiro): add GPT-5.6 Sol/Terra/Luna pricing rows

The registry additions in this PR exposed three new Kiro model ids
without matching pricing rows, tripping the catalog invariant that
every Kiro registry model must resolve a non-zero pricing row
(tests/unit/catalog-updates-v3x.test.ts) — the models would have
billed at $0.00.

Reuses the shared GPT_5_6_{SOL,TERRA,LUNA}_PRICING tiers already used
by the codex and openai aliases.

src/shared/constants/pricing/oauth-subscriptions.ts

@@ -592,5 +592,10 @@ export const DEFAULT_PRICING_OAUTH = {
       reasoning: 15.0,
       cache_creation: 3.0,
     },
+    // Kiro's GPT-5.6 family (kiro.dev/changelog/models, 2026-07-14) — same
+    // per-tier rates the codex/openai aliases already bill at.
+    "gpt-5.6-sol": GPT_5_6_SOL_PRICING,
+    "gpt-5.6-terra": GPT_5_6_TERRA_PRICING,
+    "gpt-5.6-luna": GPT_5_6_LUNA_PRICING,
   },
 };