toMarkdownPath doubles the extension for a .md path with a trailing slash

[abhay-codes07]

Summary

toMarkdownPath checks endsWith(".md") before it strips trailing slashes, so a markdown path that arrives with a trailing slash gets a doubled .md extension.

Where

packages/core/src/paths.ts:20-24

export function toMarkdownPath(pathname: string): string {
  if (pathname.endsWith(".md")) return pathname;   // "/blog/post.md/" fails this
  const trimmed = pathname.replace(/\/+$/, "");     // -> "/blog/post.md"
  if (trimmed === "") return "/index.md";
  return trimmed + ".md";                            // -> "/blog/post.md.md"
}

Reproduction

import { toMarkdownPath, toMarkdownUrl } from "@dualmark/core";

toMarkdownPath("/blog/post.md/");            // "/blog/post.md.md"  (should be "/blog/post.md")
toMarkdownUrl("https://x.com/a.md/");        // "https://x.com/a.md.md"

A request for a markdown twin with a trailing slash resolves to a nonexistent …/post.md.md and 404s. The function's own JSDoc claims idempotency on already-.md paths, and content-negotiation.md section 6 defines trailing-slash stripping for the canonical mapping.

Proposed fix

Strip trailing slashes before the .md check so an already-.md path (with or without a trailing slash) maps back to itself. PR incoming.