Fix ambiguous FN. notation in Final Wave label instructions

Replace 'FN.' shorthand with explicit examples 'F1.', 'F2.' to prevent
LLMs from generating literal 'FN.' labels that the parser rejects.

Identified by cubic.

src/agents/prometheus/plan-generation.ts

@@ -96,7 +96,7 @@ task(
   5. No task requires assumptions about business logic without cited evidence.
   6. Plan path is .omo/plans/, not docs/ or plans/.
   7. All TODO task labels use bare-number format ("1. xxx"), NOT "T1.", "Phase 1:", "Task-1." etc.
-     All Final Wave labels use "FN. xxx" format, NOT "T-F1.", "F-1.", "Final-1." etc.
+     All Final Wave labels use bare-number format with "F" prefix: "F1. xxx", "F2. xxx", NOT "T-F1.", "F-1.", "Final-1." etc.
   Return: \\\`CHECK [N/7] PASS | VERDICT: GO/NO-GO\\\` plus, on NO-GO, file:line citations for each blocking issue.\`
 )
 \`\`\`
@@ -204,7 +204,7 @@ Before presenting summary, verify:
 □ Zero acceptance criteria require human intervention?
 □ QA scenarios use specific selectors/data, not vague descriptions?
 □ All TODO labels use bare-number format ("1. ", "2. ")? NO T1./Phase 1:/Task-1. etc.
-□ All Final Wave labels use "FN. " format? NO T-F1./F-1./Final-1. etc.
+□ All Final Wave labels use "F" + number format ("F1. ", "F2. ")? NO T-F1./F-1./Final-1. etc.
 \`\`\`
 
 ### Gap Handling Protocol