feat: remove support for XEZIM and CVC simulators

- Deleted references to XEZIM and CVC in the Makefile and related scripts.
- Removed XEZIM-specific and CVC-specific files, including external memory models and SRAM models.
- Updated the test suite to reflect the removal of XEZIM and CVC simulators, ensuring no broken references remain.
- Cleaned up the README and doctor scripts to remove mentions of XEZIM and CVC.

scripts/README.md

@@ -13,11 +13,6 @@ entry point. It installs only the checksum-verified open-source tool bundles and
 hash-pinned Python dependencies; project-local PDK and source setup remains under
 the existing Make targets.
 
-The optional `XEZIM` and `CVC` simulator backends are intentionally not part of
-that locked installer. `scripts/doctor.py` checks them when `SIMU=XEZIM` or
-`SIMU=CVC` is selected and resolves the executable from the corresponding
-`XEZIM` or `CVC` environment variable.
-
 `publish_fatfs_artifact.sh` is the manual release helper for the lock-pinned
 FatFs R0.16 archive. It verifies the archive, GitHub authentication, release
 absence, and the published asset checksum before reporting the checksum-pinned

scripts/doctor.py

@@ -4,7 +4,6 @@ from __future__ import annotations
 
 import argparse
 import json
-import os
 import shutil
 import subprocess
 import sys
@@ -41,9 +40,6 @@ def version(executable: str) -> str | None:
         "iverilog": "-V",
         "vvp": "-V",
         "sta": "-version",
-        "xezim": "-V",
-        "cvc": "-h",
-        "cvc64": "-h",
     }
     result = subprocess.run(
         [executable, options.get(name, "--version")],
@@ -66,10 +62,6 @@ def main() -> int:
         tools.extend(("verilator", "c++"))
     elif args.simu == "VCS":
         tools.extend(("bsub", "vcs"))
-    elif args.simu == "XEZIM":
-        tools.append(os.environ.get("XEZIM", "xezim"))
-    elif args.simu == "CVC":
-        tools.append(os.environ.get("CVC", "cvc"))
     if args.synth == "YOSYS":
         tools.append("yosys")
     if args.sta == "OPENSTA":