Add Power C disk image, manuals, and work disk

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
1 week ago · 770084770c
--- a/examples/powerc-work.d81
+++ b/examples/powerc-work.d81
--- a/reference/POWERc.d81
+++ b/reference/POWERc.d81
--- a/reference/Power_C_Instruction_Manual.pdf
+++ b/reference/Power_C_Instruction_Manual.pdf
--- a/reference/vice.pdf
+++ b/reference/vice.pdf