Add BIOS and tiny kernel roadmap phases

Tutorial/phase-04-first-cpu/phase-04-01-fetch-datapath-integration.md

@@ -27,7 +27,7 @@ more than minimizing cycles.
 
 - Write a cycle-by-cycle timeline for a simple `addi` instruction.
 - Write a cycle-by-cycle timeline for a multiply/divide instruction.
-- Confirm the pre-Phase 9 illegal-instruction behavior: halt the core and expose
+- Confirm the pre-Phase 12 illegal-instruction behavior: halt the core and expose
   the offending PC and instruction word to the testbench.
 
 ## Pitfalls