test(ci): demote the preamble A/B to periodic (OV7) and add it to the periodic matrix

Post-Phase-3 demotion per the plan; the eval needs fetch-depth 0 (it git
shows a pre-Phase-1 sha), which only the periodic workflow provides — and
a static matrix entry so it can't silently never run.

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

test/helpers/touchfiles-data.ts

@@ -540,7 +540,7 @@ export const E2E_TIERS: Record<string, 'gate' | 'periodic'> = {
   // Real-PTY E2E batch — tier classification:
   //   gate: cheap, deterministic, run on every PR
   //   periodic: long-running or expensive (>$3/run), run weekly
-  'preamble-script-ab':                      'gate',       // Phase 1-3 A/B: script vs inline preamble; demote to periodic after Phase 3 (OV7)
+  'preamble-script-ab':                      'periodic',   // Phase 1-3 A/B: script vs inline preamble; demoted post-Phase-3 (OV7)
   'auq-format-gate':                         'gate',       // ~$0.50/run, SDK capture, single skill probe
   'plan-ceo-mode-routing':     'periodic',   // ~$3/run, deep navigation through 8-12 prior AskUserQuestions
   'plan-design-with-ui-scope': 'gate',       // ~$0.80/run

test/skill-e2e-preamble-script-ab.test.ts

@@ -33,7 +33,7 @@ import {
   carvedSkill,
 } from './helpers/auq-sdk-capture';
 
-const describeE2E = describeE2ETier('gate');
+const describeE2E = describeE2ETier('periodic');
 const runId = `preamble-ab-${process.env.EVALS_RUN_ID ?? 'local'}`;
 const ROOT = path.resolve(import.meta.dir, '..');
 const INLINE_REF = '29785978'; // last pre-Phase-1 commit (v1.69.1.0 bump)