fix: run the read-only tools from the repo root

Only verify.py and generate_pack.py moved to the repository root. From
any other folder slots, region_audit, provenance_report and bundled_only
said database.json was missing and to rebuild it, identity and
list_platforms named a missing folder, and game_rules ended on a
FileNotFoundError traceback. work_from_repo_root moves to common.py and
the eight tools call it: defaults are read from the root, a path the
user typed from where it was typed.

scripts/common.py

@@ -9,6 +9,7 @@ from __future__ import annotations
 from collections.abc import Callable, Iterable
 from collections import Counter
 
+import argparse
 import filecmp
 import hashlib
 import functools
@@ -670,6 +671,31 @@ def suggest_names(
     return f"{listing_flag} lists all {total}."
 
 
+def work_from_repo_root(
+    args: argparse.Namespace, parser: argparse.ArgumentParser, path_flags: list[str]
+) -> None:
+    """Run from the repository root, whichever directory the command started in.
+
+    database.json records every file from the root and the data registry
+    names its caches the same way, so a run from scripts/ ended on a
+    FileNotFoundError traceback. A path the caller typed is read from where
+    they typed it, a default from the root.
+    """
+    root = Path(__file__).resolve().parent.parent
+    if Path.cwd().resolve() == root:
+        return
+    for flag in path_flags:
+        value = getattr(args, flag, None)
+        if value and value != parser.get_default(flag):
+            # A Path stays a Path for the code that joins onto it.
+            setattr(args, flag, type(value)(os.path.abspath(value)))
+    os.chdir(root)
+    if getattr(args, "platform", None):
+        # Read before the move, the registry was not there to map
+        # "RetroArch" to its slug.
+        args.platform = platform_arg(args.platform)
+
+
 def platform_arg(value: str) -> str:
     """--platform as typed, mapped to the registry's slug when it names one.