docs: add companies frontmatter, schema, and rendering in badges & appendix pages

apps/docs/blume.config.ts

@@ -2,6 +2,7 @@ import { defineConfig } from "blume";
 import type { StandardSchema } from "blume/core/standard-schema.ts";
 import { filesystem } from "blume/sources";
 import { APPENDIX } from "./appendix";
+import { RECENCY, type Company } from "./companies";
 import redirects from "./redirects";
 
 // Blume's defaults (`inter`, `ibm-plex-mono`) are fetched from fonts.gstatic.com
@@ -33,13 +34,14 @@ const plexMono = {
 };
 
 /**
- * Custom frontmatter, rendered as the badge row by
+ * Custom frontmatter, rendered between the description and the body by
  * components/ProblemBadges.astro. Problem pages: `topics:` is LeetCode's topic
- * tags and `issue:` the problem's GitHub issue URL (both written by
- * apps/cli/sync.ts), `video:` the NeetCode walkthrough's
- * YouTube id (apps/cli/videos.ts). Blume rejects undeclared keys and takes
- * any Standard Schema; these are hand-rolled so the docs workspace needs no
- * zod. All optional — every other page carries none.
+ * tags, `issue:` the problem's GitHub issue URL and `companies:` the companies
+ * that asked it in the last six months (`companies.ts`; the table under the
+ * badge row) — all three written by apps/cli/sync.ts — and `video:` the
+ * NeetCode walkthrough's YouTube id (apps/cli/videos.ts). Blume rejects
+ * undeclared keys and takes any Standard Schema; these are hand-rolled so the
+ * docs workspace needs no zod. All optional — every other page carries none.
  */
 const optional = <T>(
   message: string,
@@ -74,6 +76,17 @@ const issueSchema = optional(
     typeof value === "string" &&
     /^https:\/\/github\.com\/[\w.-]+\/[\w.-]+\/issues\/\d+$/.test(value),
 );
+const companiesSchema = optional(
+  `expected a list of { name, period, frequency } with period one of ${RECENCY.join(" | ")}`,
+  (value): value is Company[] =>
+    Array.isArray(value) &&
+    value.every(
+      (c) =>
+        typeof c?.name === "string" &&
+        RECENCY.includes(c?.period) &&
+        typeof c?.frequency === "number",
+    ),
+);
 
 export default defineConfig({
   title: "prdlk",
@@ -102,6 +115,7 @@ export default defineConfig({
       topics: topicsSchema,
       video: videoSchema,
       issue: issueSchema,
+      companies: companiesSchema,
     },
   },
   seo: {