Add a footer and an in-app docs viewer

Footer (in the authenticated app layout, matching where Nav lives):
copyright line, a Docs link, and a link to the project repo.

Docs viewer: /docs lists docs/API.md, CONFIG_REFERENCE.md, and
ARCHITECTURE.md; /docs/[slug] renders one via react-markdown +
remark-gfm (tables, fenced code) inside a Tailwind Typography `prose`
block, dark-mode aware via prose-invert. The markdown files themselves
stay the single source of truth at the repo's docs/ - the app reads
them at request time rather than duplicating their content, resolved
from the app's cwd the same way config paths already are, since a
compiled Route Handler's module graph doesn't preserve source-relative
paths.

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

app/src/lib/docs.ts

@@ -0,0 +1,47 @@
+import fs from "node:fs";
+import path from "node:path";
+
+export interface DocMeta {
+  slug: string;
+  title: string;
+  description: string;
+  file: string;
+}
+
+export const DOCS: DocMeta[] = [
+  {
+    slug: "api",
+    title: "API Reference",
+    description: "REST and WebSocket endpoints, auth, and request/response shapes.",
+    file: "API.md",
+  },
+  {
+    slug: "config",
+    title: "Config Reference",
+    description: "Every field in triggershell.yml: server, auth, scripts, and variables.",
+    file: "CONFIG_REFERENCE.md",
+  },
+  {
+    slug: "architecture",
+    title: "Architecture",
+    description: "How the CLI, custom server, runner, and web app fit together.",
+    file: "ARCHITECTURE.md",
+  },
+];
+
+export function getDocMeta(slug: string): DocMeta | undefined {
+  return DOCS.find((doc) => doc.slug === slug);
+}
+
+// docs/ ships at the repo root, one level up from this Next app - resolved at runtime rather
+// than imported, since the compiled Route Handler module graph doesn't preserve source-relative
+// paths (same reasoning as config path resolution in lib/config/load.ts).
+function docsDir(): string {
+  return path.resolve(process.cwd(), "..", "docs");
+}
+
+export function readDocContent(doc: DocMeta): string | null {
+  const filePath = path.join(docsDir(), doc.file);
+  if (!fs.existsSync(/*turbopackIgnore: true*/ filePath)) return null;
+  return fs.readFileSync(/*turbopackIgnore: true*/ filePath, "utf-8");
+}