test: move the full office-hours workflow to marathon; add a periodic design-draft checkpoint

The full startup workflow runs 1–3 real spec-review rounds (~280s each) and
hit its 1200s capture in run 36385945043 at finalize. Review depth is the
product's loop, so the case cannot fit a blocking lane without cutting
rounds. It is now marathon tier with every assertion unchanged.

skill-e2e-office-hours-design-draft.test.ts (periodic) runs the same fixed
interview only through the Write that creates the design (269s in that run)
and applies the full validator's design-draft checks, the required section
reads and the launch/foreign-skill-read guards. validateOfficeHoursDesignDraft
is extracted from validateOfficeHoursCompletion, which still applies it.

Selection: office-hours-design-draft is registered periodic; the marathon-only
file is already excluded from the gate and periodic plans by the B5 planner
rule. Tier-alignment regexes and the valid-tier check accept 'marathon'.
A type-only cast in plan-scope-selection.test.ts removes a diagnostic whose
union print order made the ratchet identity unstable; baseline tightened.

test/touchfiles.test.ts

@@ -510,7 +510,7 @@ describe('TOUCHFILES completeness', () => {
   });
 
   test('E2E_TIERS only contains valid tier values', () => {
-    const validTiers = ['gate', 'periodic'];
+    const validTiers = ['gate', 'periodic', 'marathon'];
     for (const [name, tier] of Object.entries(E2E_TIERS)) {
       if (!validTiers.includes(tier)) {
         throw new Error(`E2E_TIERS['${name}'] has invalid tier '${tier}'. Valid: ${validTiers.join(', ')}`);