feat: gate mentor auto-assign on CONFIRMED finalist status

mentor.autoAssignBulkForRound now skips any project whose finalist
confirmation isn't CONFIRMED — there's no point assigning a mentor to
a team that won't be at the grand finale. Other eligibility rules
(wantsMentorship, admin_selected, already-assigned) are preserved.

Updated existing requested_only and skip-already-assigned tests to seed
CONFIRMED confirmations so they continue to isolate their target gate.

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

src/server/routers/mentor.ts

@@ -717,6 +717,10 @@ export const mentorRouter = router({
           roundId: input.roundId,
           project: {
             mentorAssignment: null,
+            // Only assign mentors to projects whose team has confirmed they will
+            // attend the grand finale. This skips PENDING/DECLINED/EXPIRED/SUPERSEDED
+            // confirmations and any project without a confirmation row at all.
+            finalistConfirmation: { status: 'CONFIRMED' },
             ...(eligibility === 'requested_only' ? { wantsMentorship: true } : {}),
           },
         },