feat(storage): resolve portable workspace roots

harness/tht/paths.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+from tht.config import ConfigError
+
+if TYPE_CHECKING:
+    from tht.config import Config
+
+
+@dataclass(frozen=True)
+class ResolvedPaths:
+    workspace: Path
+    sessions: Path
+    artifacts: Path
+    indexes: Path
+    corpus: Path
+
+
+def _resolve_root(path: Path, workspace: Path, name: str) -> Path:
+    if path.is_absolute():
+        # Existing deployments commonly point at an external workspace checkout. Keep
+        # those paths working while `tht doctor` identifies them for migration.
+        return path
+
+    resolved = (workspace / path).resolve()
+    if not resolved.is_relative_to(workspace):
+        raise ConfigError(f"paths.{name} resolves outside workspace root")
+    return resolved
+
+
+def resolve_workspace_paths(
+    config_path: Path, cfg: Config, data_root: Path
+) -> ResolvedPaths:
+    """Resolve portable paths under ``<data_root>/workspaces/<config stem>``.
+
+    Relative roots are sandboxed to the logical workspace. Absolute roots are a
+    compatibility bridge for existing installations and are never rewritten.
+    """
+    workspace = (data_root / "workspaces" / config_path.stem).resolve()
+    roots = cfg.roots
+    return ResolvedPaths(
+        workspace=workspace,
+        sessions=_resolve_root(roots.sessions, workspace, "sessions"),
+        artifacts=_resolve_root(roots.artifacts, workspace, "artifacts"),
+        indexes=_resolve_root(roots.indexes, workspace, "indexes"),
+        corpus=(workspace / "corpus").resolve(),
+    )