Remove the image build and consolidate operational code under scripts

scripts/engine/descriptor.py

@@ -0,0 +1,77 @@
+# scripts/engine/descriptor.py
+"""Declarative action descriptors — successor to the bash action_metadata() heredoc.
+
+Meta drives BOTH the help text and argparse parsing. Exit code 64 (EX_USAGE) on a
+usage error, matching the bash engine.
+"""
+from __future__ import annotations
+
+import argparse
+from dataclasses import dataclass, field
+from typing import List
+
+
+class _Parser(argparse.ArgumentParser):
+    """ArgumentParser that exits 64 (EX_USAGE) instead of 2 on a usage error."""
+
+    def error(self, message: str):
+        self.print_usage()
+        self.exit(64, f"{self.prog}: error: {message}\n")
+
+
+@dataclass
+class Arg:
+    """A positional argument. required=False -> optional positional (default None)."""
+    name: str
+    help: str = ""
+    required: bool = True
+
+    def add_to(self, p: argparse.ArgumentParser) -> None:
+        if self.required:
+            p.add_argument(self.name, help=self.help)
+        else:
+            p.add_argument(self.name, nargs="?", default=None, help=self.help)
+
+
+@dataclass
+class Opt:
+    """An optional value flag, e.g. --tier PATH, with a default."""
+    name: str
+    help: str = ""
+    default: object = None
+
+    def add_to(self, p: argparse.ArgumentParser) -> None:
+        p.add_argument(self.name, default=self.default, help=self.help)
+
+
+@dataclass
+class Flag:
+    """A boolean flag, e.g. --dry-run (store_true)."""
+    name: str
+    help: str = ""
+
+    def add_to(self, p: argparse.ArgumentParser) -> None:
+        p.add_argument(self.name, action="store_true", help=self.help)
+
+
+@dataclass
+class Rest:
+    """Greedy passthrough of all remaining argv (argparse.REMAINDER)."""
+    name: str
+    help: str = ""
+
+    def add_to(self, p: argparse.ArgumentParser) -> None:
+        p.add_argument(self.name, nargs=argparse.REMAINDER, help=self.help)
+
+
+@dataclass
+class Meta:
+    summary: str
+    args: List[object] = field(default_factory=list)
+
+
+def build_parser(meta: Meta, prog: str) -> argparse.ArgumentParser:
+    p = _Parser(prog=prog, description=meta.summary)
+    for a in meta.args:
+        a.add_to(p)
+    return p