feat: complete MENTORING round config form (§A)

Surfaces every MentoringConfigSchema field on the round Config tab:

- Adds "Mentoring Request Window" card with mentoringRequestDeadlineDays
  numeric input (1-90 days, default 14) and passThroughIfNoRequest toggle
  (default ON; OFF holds projects PENDING until manual mentor assignment).
- Adds inline help-text for the Eligibility dropdown explaining each
  option's effect on auto-PASS behavior.
- Hides the General Settings card on MENTORING rounds (it only renders
  Advancement Targets, which don't apply to a pass-through round).
- Relaxes the Launch Readiness "File requirements set" gate for MENTORING
  rounds without filePromotionEnabled + a target window — file requirements
  only matter when files will be promoted to a downstream submission window.

Spec: docs/superpowers/specs/2026-04-28-mentor-round-readiness-design.md §A
Plan: docs/superpowers/plans/2026-04-28-pr3-mentoring-config-completeness.md

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/(admin)/admin/rounds/[roundId]/page.tsx

@@ -514,6 +514,7 @@ export default function RoundDetailPage() {
 
   const isFiltering = round?.roundType === 'FILTERING'
   const isEvaluation = round?.roundType === 'EVALUATION'
+  const isMentoring = round?.roundType === 'MENTORING'
   const hasJury = ['EVALUATION', 'LIVE_FINAL', 'DELIBERATION'].includes(round?.roundType ?? '')
   const hasAwards = roundAwards.length > 0
   const isSimpleAdvance = ['INTAKE', 'SUBMISSION', 'MENTORING'].includes(round?.roundType ?? '')
@@ -589,7 +590,8 @@ export default function RoundDetailPage() {
       action: undefined as Route | undefined,
       actionLabel: undefined as string | undefined,
     },
-    ...((isEvaluation && !(config.requireDocumentUpload as boolean))
+    ...((isEvaluation && !(config.requireDocumentUpload as boolean)) ||
+      (isMentoring && !(config.filePromotionEnabled as boolean) && !config.promotionTargetWindowId)
       ? []
       : [{
           label: 'File requirements set',
@@ -2198,7 +2200,8 @@ export default function RoundDetailPage() {
             </CardContent>
           </Card>
 
-          {/* General Round Settings */}
+          {/* General Round Settings — hidden on MENTORING rounds (no advancement targets apply) */}
+          {!isMentoring && (
           <Card>
             <CardHeader className="border-b">
               <ConfigSectionHeader
@@ -2321,6 +2324,7 @@ export default function RoundDetailPage() {
               )}
             </CardContent>
           </Card>
+          )}
 
           {/* Round-type-specific config */}
           <RoundConfigForm