P120 - PRF rename sketch

P120 adds a shadow integer physical-register-file rename map. It does not change architectural register behavior; regs[] remains the real machine state.

The shell profile is PASS:

post-load cycles    : 219,108,349
shell window cycles : 65,160,251
retired instructions: 86,463,913
CPI                 : 2.5341
S_FETCH cycles      : 7,631,468
S_MEM cycles        : 27,805,129

PRF sketch counters:

source reads      : 147,100,017
destinations seen : 79,682,431
allocs            : 59,313,939
frees             : 59,313,939
commits           : 59,313,939
live at end       : 32
max live          : 32

Honest status: RTL simulation PASS. LibreLane hardening is NOT RUN.