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/plan-scope-selection.test.ts

@@ -320,7 +320,7 @@ test('new scope route rejects stale, foreign, premature or unsuccessful evidence
     p => { p.tools[1]!.toolUseId = 'unrelated'; },
     p => { p.tools[1]!.sessionId = 'foreign'; },
     p => { p.tools.splice(1, 1); },
-    p => { p.tools.push(structuredClone(p.tools[1]!)); },
+    p => { p.tools.push(structuredClone(p.tools[1]!) as never); },
     p => { p.tools[2]!.timestamp = new Date(p.opts.commandStartedAt + 1).toISOString(); },
     p => { p.tools[2]!.timestamp = new Date(Date.parse(p.tools[1]!.timestamp) - 1).toISOString(); },
     p => { p.tools[2]!.timestamp = 'unknown'; },