refactor(test): migrate the 36 tier-gated eval files to describeE2ETier

Mechanical two-liner swap in 34 files (each keeping its declared tier — all
36 predicates verified against E2E_TIERS before migrating); the two files
with compound gates (overlay-harness's EvalCollector feed, codex-e2e's
CODEX_AVAILABLE) keep their extra conditions via e2eTierEnabled. Tier
rationale comments preserved. codex-e2e/gemini-e2e/benchmark-providers keep
their distinct stderr-message gate shapes by design.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/codex-e2e-recommendation-substance.test.ts

@@ -22,6 +22,7 @@
  */
 import { describe, test, expect } from 'bun:test';
 import * as path from 'node:path';
+import { e2eTierEnabled } from './helpers/e2e-gate';
 import { runCodexSkill } from './helpers/codex-session-runner';
 import { judgeRecommendation } from './helpers/llm-judge';
 
@@ -34,8 +35,7 @@ const CODEX_AVAILABLE = (() => {
     return false;
   }
 })();
-const shouldRun =
-  CODEX_AVAILABLE && !!process.env.EVALS && process.env.EVALS_TIER === 'periodic';
+const shouldRun = CODEX_AVAILABLE && e2eTierEnabled('periodic');
 const describeCodex = shouldRun ? describe : describe.skip;
 
 // A small fixture with two real, comparable problems so a good recommendation