fix(fs): do not parse relative paths with a colon as URLs (#3632)

In plugins/fs/src/file_path.rs SafeFilePath::from_str, any string that
parsed as a URL with a scheme of 2+ characters was a URL, so a relative
path such as `notes:2024.txt` became a cannot-be-a-base URL and failed
with InvalidPathUrl.

Cannot-be-a-base URLs are now parsed as paths. The scheme-agnostic
url.to_file_path() stays: its result is scope checked (not a bypass).
Unit test for the parser; e2e spec writes and reads such a file (not on
Windows, where `:` is not allowed in file names).

plugins/fs/src/file_path.rs

@@ -203,7 +203,9 @@ impl FromStr for SafeFilePath {
     type Err = Error;
     fn from_str(s: &str) -> Result<Self> {
         if let Ok(url) = url::Url::from_str(s)
-            && url.scheme().len() != 1
+            // single letter schemes are Windows drive letters, and URLs that cannot be a base
+            // (no `//` nor `/` after the scheme) are relative paths such as `notes:2024.txt`
+            && url.scheme().len() != 1 && !url.cannot_be_a_base()
         {
             return Ok(Self::Url(url));
         }
@@ -306,3 +308,39 @@ impl TryFrom<FilePath> for SafeFilePath {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::str::FromStr;
+
+    use super::SafeFilePath;
+
+    #[test]
+    fn safe_file_path_from_str() {
+        for url in [
+            "file:///C:/Users",
+            "file:///home/user/file.txt",
+            "content://com.android.providers/document/1",
+            "asset://localhost/file.txt",
+        ] {
+            assert!(
+                matches!(SafeFilePath::from_str(url), Ok(SafeFilePath::Url(_))),
+                "{url}"
+            );
+        }
+
+        for path in [
+            "C:/Users",
+            "C:\\Users",
+            "notes:2024.txt",
+            "ab:c",
+            "dir/file.txt",
+            "/home/user/file.txt",
+        ] {
+            assert!(
+                matches!(SafeFilePath::from_str(path), Ok(SafeFilePath::Path(_))),
+                "{path}"
+            );
+        }
+    }
+}