Make the repository's primary source tree genuinely Python

The old tracked TypeScript snapshot has been removed from the repository history and the root  directory is now a Python porting workspace. README and tests now describe and verify the Python-first layout instead of treating the exposed snapshot as the active source tree.

A local archive can still exist outside Git, but the tracked repository now presents only the Python porting surface, related essay context, and OmX workflow artifacts.

Constraint: Tracked history should collapse to a single commit while excluding the archived snapshot from Git
Rejected: Keep the exposed TypeScript tree in tracked history under an archive path | user explicitly wanted only the Python porting repo state in Git
Confidence: medium
Scope-risk: broad
Reversibility: messy
Directive: Keep future tracked additions focused on the Python port itself; do not reintroduce the exposed snapshot into Git history
Tested: python3 -m unittest discover -s tests -v; python3 -m src.main summary; git diff --check
Not-tested: Behavioral parity with the original TypeScript system beyond the current Python workspace surface

src/models.py

@@ -0,0 +1,31 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+
+
+@dataclass(frozen=True)
+class Subsystem:
+    name: str
+    path: str
+    file_count: int
+    notes: str
+
+
+@dataclass(frozen=True)
+class PortingModule:
+    name: str
+    responsibility: str
+    source_hint: str
+    status: str = 'planned'
+
+
+@dataclass
+class PortingBacklog:
+    title: str
+    modules: list[PortingModule] = field(default_factory=list)
+
+    def summary_lines(self) -> list[str]:
+        return [
+            f'- {module.name} [{module.status}] — {module.responsibility} (from {module.source_hint})'
+            for module in self.modules
+        ]