Add language percentages to repo pages

GitHub no longer server-renders the repository sidebar; its React UI
lazily fetches /:owner/:repo/_sidebar as JSON, which carries the
language breakdown (name, percentage, color). getGitHubLanguages() uses
that endpoint, and a new /api/:owner/:repo/languages fragment route
renders the bar and legend the same way refs and latest-commit already
work, so repo page loads still cost a single scrape.

The latest-commit placeholder loader in refs.js is generalized over
.placeholder[data-src] so both placeholders share it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/app.ts b/src/app.ts
index ca79b1f..e34c7b1 100644
--- a/src/app.ts
+++ b/src/app.ts
@@ -5,6 +5,7 @@ import {
   getGitHubBlob,
   getGitHubCommits,
   getGitHubIssues,
+  getGitHubLanguages,
   getGitHubLatestCommit,
   getGitHubOwner,
   getGitHubPulls,
@@ -158,6 +159,11 @@ export function createApp(eta: Eta) {
     );
   });
 
+  app.get("/api/:owner/:repo/languages", async (c) => {
+    const { owner, repo } = c.req.param();
+    return tryRenderFragment(c, "_languages.eta", getGitHubLanguages(owner, repo));
+  });
+
   app.get("/:owner/:repo/releases/tag/:tag", async (c) => {
     const { owner, repo, tag } = c.req.param();
     return tryRender(c, "release.eta", getGitHubRelease(owner, repo, tag));