1.0 quality polish — code review, tests, bug fixes, documentation (#32)

Comprehensive quality pass targeting 1.0 release:

- Code review and refactoring
- Fix open bugs (#14, #16, #23)
- Expand test coverage
- Lint clean
- README update with build instructions (#9)
- Documentation improvements

Branched from `next` (active dev branch).

Reviewed-on: #32
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

mfer/url.go

@@ -27,8 +27,12 @@ func (b BaseURL) JoinPath(path RelFilePath) (FileURL, error) {
 		base.Path += "/"
 	}
 
-	// Parse and encode the relative path
-	ref, err := url.Parse(url.PathEscape(string(path)))
+	// Encode each path segment individually to preserve slashes
+	segments := strings.Split(string(path), "/")
+	for i, seg := range segments {
+		segments[i] = url.PathEscape(seg)
+	}
+	ref, err := url.Parse(strings.Join(segments, "/"))
 	if err != nil {
 		return "", err
 	}