refactor: consolidate host-side C++ into a clean sim/ tree

[HirunaVishwamith]

Summary

Reorganizes the host-side C++ — golden-model emulator, Verilator wrapper, and lock-step/profile harnesses — from three scattered top-level trees (emulator/, simulator/src/, harnesses/) into one coherent sim/ tree. Behavior-preserving: the ISA regression stays 83/84 (same sole failure, rv64ui-p-fence_i) and vvadd-q4 PASS at every step.

Structure

Old	New
emulator/src/	sim/emulator/
simulator/src/	sim/rtl/
simulator/src/simulator.h	sim/rtl/rtl_model.h
harnesses/	sim/harness/
emulator/riscv-tests/	sim/tests/riscv-isa/
Image / qemu.dtb / boot.bin	sim/data/

Cleanups

• Split the 2231-line hart.h into a ~340-line table-of-contents plus hart_{csr,trap,alu,memory,execute}.inc fragments, each #included at its exact original location (token-identical after preprocessing, so lock-step is provably unchanged). Free TTY helpers → terminal.h; include guard added to clint.h.
• Deduped harness boilerplate (arg parsing, image loading, completion checks) into sim/harness/common/{args,image,completion}.h under namespace harness.
• Rewrote rtl_model.h: added the missing include guard, replaced four hand-unrolled 32-case register switch ladders with a table-driven reg(i), merged the near-duplicate step/step_nodump, dropped commented-out dead code.
• Deleted dead files: emulator-v1.h (1883 lines), rv_tests.cpp, bench.cpp, run.sh, simulator.txt, bbl_nommu.dump, format.gtkw, support_prog.cpp, the redundant standalone emulator/Makefile, and committed build artifacts.
• Fixed a pre-existing bug: make emu never worked (emulator_linux.cpp ignored argv and opened a non-existent default Image); it now honors argv[1].
• Rewired mk/config.mk + mk/run.mk paths, consolidated .gitignore, updated the README layout. CI is unchanged (it drives everything through make).

Verification

Check	Result
make isa	83/84 — identical to baseline
make test-q4	vvadd-q4 PASS
make runLockStep	vvadd-s1 pass
make profile BENCH=vvadd-s1	completes + JSON written
make emu BENCH=vvadd-s1	runs (now fixed)
All 7 harnesses	compile clean, no warnings

make clean && make sim (full sbt+Verilator rebuild) was intentionally not run locally since the RTL is untouched — CI exercises that path.

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