fix(scripts): improve usability across all ADR-061 QEMU testing scripts

- Add --help/-h flags to all 4 shell scripts with usage, env vars, examples
- Add prerequisite checks with install hints (apt/brew/pip) for missing tools
- Standardize exit codes (0=PASS, 1=WARN, 2=FAIL, 3=FATAL) across all scripts
- Standardize MESH_TIMEOUT to QEMU_TIMEOUT with backward compatibility
- Add SKIP_BUILD precheck for missing flash image in qemu-esp32s3-test.sh
- Add argparse to validate_qemu_output.py (was using raw sys.argv)
- Improve error messages in generate_nvs_matrix.py with NVS tool install hints
- Add socket connection warnings in inject_fault.py connect_monitor()
- Add example output epilog to check_health.py --help
- Add glossary (14 terms) and quick-start section to ADR-061
- Add GDB debugging walkthrough to ADR-061 Layer 4
- Fix stat portability in CI workflow (stat -c%s -> portable file_size())
- Add -type f to find commands in CI workflow

Co-Authored-By: claude-flow <ruv@ruv.net>

scripts/validate_qemu_output.py

@@ -16,6 +16,7 @@ Exit codes:
     3  Fatal (crash or corruption detected)
 """
 
+import argparse
 import re
 import sys
 from dataclasses import dataclass, field
@@ -364,11 +365,18 @@ def validate_log(log_text: str) -> ValidationReport:
 
 
 def main():
-    if len(sys.argv) < 2:
-        print(f"Usage: {sys.argv[0]} <log_file>", file=sys.stderr)
-        sys.exit(3)
+    parser = argparse.ArgumentParser(
+        description="Validate QEMU ESP32-S3 UART output (ADR-061)",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        epilog="Example: python3 validate_qemu_output.py build/qemu_output.log",
+    )
+    parser.add_argument(
+        "log_file",
+        help="Path to QEMU UART log file",
+    )
+    args = parser.parse_args()
 
-    log_path = Path(sys.argv[1])
+    log_path = Path(args.log_file)
     if not log_path.exists():
         print(f"ERROR: Log file not found: {log_path}", file=sys.stderr)
         sys.exit(3)