Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

infra/perf-monitor/src/github.ts

@@ -0,0 +1,77 @@
+/**
+ * GitHub API helpers for resolving a commit SHA to a merged PR number.
+ *
+ * Uses the "list pull requests associated with a commit" endpoint:
+ * https://docs.github.com/en/rest/commits/commits#list-pull-requests-associated-with-a-commit
+ *
+ * Called unauthenticated. The public repo endpoint has a 60 req/hr limit per IP,
+ * which is far more than our deploy rate. If that ever changes, add a token:
+ * `headers.authorization = "Bearer " + env.GITHUB_TOKEN`.
+ */
+
+import { GITHUB_REPO } from "./routes.js";
+
+interface AssociatedPR {
+	number: number;
+	state: string;
+	merged_at: string | null;
+	base: { ref: string };
+}
+const PR_NUMBER_REGEX = /\(#(\d+)\)\s*$/;
+/**
+ * Parse a PR number from a commit message. GitHub squash merges append the PR
+ * number in parentheses, e.g. "feat: add feature (#123)".
+ */
+function parsePrFromMessage(commitMessage: string): number | null {
+	const match = commitMessage.match(PR_NUMBER_REGEX);
+	if (!match?.[1]) return null;
+	return parseInt(match[1], 10);
+}
+
+/**
+ * Find the merged PR for a given commit SHA, if any.
+ *
+ * Strategy:
+ * 1. Parse the commit message for `(#N)` — works for squash merges (the common case).
+ * 2. Fall back to the GitHub "list PRs for a commit" API — works for merge commits.
+ *
+ * Returns null if no PR exists (e.g. direct push to main) or the lookup fails.
+ */
+export async function resolvePrForSha(sha: string, commitMessage?: string): Promise<number | null> {
+	if (commitMessage) {
+		const fromMessage = parsePrFromMessage(commitMessage);
+		if (fromMessage) return fromMessage;
+	}
+
+	const url = `https://api.github.com/repos/${GITHUB_REPO}/commits/${sha}/pulls`;
+
+	let response: Response;
+	try {
+		response = await fetch(url, {
+			headers: {
+				accept: "application/vnd.github+json",
+				"user-agent": "emdash-perf-monitor",
+				"x-github-api-version": "2022-11-28",
+			},
+		});
+	} catch (err) {
+		console.error("PR lookup failed:", err);
+		return null;
+	}
+
+	if (!response.ok) {
+		console.warn(`PR lookup for ${sha} returned ${response.status}`);
+		return null;
+	}
+
+	const prs = await response.json<AssociatedPR[]>();
+
+	// Prefer a merged PR targeting main. Fall back to any merged PR.
+	const mainPr = prs.find((p) => p.merged_at && p.base.ref === "main");
+	if (mainPr) return mainPr.number;
+
+	const anyMerged = prs.find((p) => p.merged_at);
+	if (anyMerged) return anyMerged.number;
+
+	return null;
+}