Reject paths in .tool-versions (#1007)

## Summary
- reject path-like uv versions from `.tool-versions`
- reject path-like Python versions from `.tool-versions`
- document the restriction and cover Unix and Windows paths in tests

## Testing
- `npm ci --ignore-scripts`
- `npm run all`

Refs: pi-session 019ff4bb-8b7c-7c4b-8bdf-7c188dfa2e3f

dist/save-cache/index.cjs

@@ -61862,7 +61862,7 @@ function getPythonVersionFromToolVersions(filePath) {
     return void 0;
   }
   const version3 = stripVersionPrefix(versions[0]);
-  if (version3 === "system" || version3.startsWith("ref:") || version3.startsWith("path:")) {
+  if (version3 === "system" || version3.startsWith("ref:") || version3.startsWith("path:") || isPath(version3)) {
     warning(
       `The Python version ${versions[0]} in .tool-versions is not supported. The Python entry will be ignored.`
     );
@@ -61890,6 +61890,9 @@ function getToolVersions(filePath, toolName) {
 function stripVersionPrefix(version3) {
   return version3.startsWith("v") ? version3.slice(1) : version3;
 }
+function isPath(version3) {
+  return version3.includes("/") || version3.includes("\\");
+}
 
 // src/utils/config-file.ts
 var import_node_fs3 = __toESM(require("node:fs"), 1);