Flatten the repo: move everything out of app/ to the root

Now that the CLI and the Next.js app are one package, nesting it inside
app/ served no purpose - the repo root itself becomes the published
npm package. Merges app/.gitignore and app/README.md into the root
versions, drops the now-duplicate app/LICENSE, and updates path
references (README, docs/ARCHITECTURE.md, docs/CONFIG_REFERENCE.md,
package.json's repository.directory) that assumed the app/ nesting.

Also fixes a real bug this surfaced: the in-app docs viewer resolved
docs/ relative to process.cwd(), which only worked by accident when the
CLI happened to be invoked from app/'s parent directory. A first attempt
at fixing it with import.meta.dirname broke instead, for the same
cross-module-graph reason config-path resolution already documented -
Next compiles Route Handlers through a separate module graph that
doesn't preserve source-relative import.meta paths. Fixed by exposing
the app root via TRIGGERSHELL_APP_ROOT (set once in server.ts, where
import.meta *does* resolve correctly), the same pattern already used
for TRIGGERSHELL_CONFIG_PATH.

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

src/proxy.ts

@@ -0,0 +1,54 @@
+import { NextResponse } from "next/server";
+import type { NextRequest } from "next/server";
+import { getConfig } from "@/lib/config/load";
+import { verifySessionCookieValue } from "@/lib/auth/session";
+
+const PUBLIC_PATHS = [
+  "/login",
+  "/api/auth/login",
+  "/api/auth/session",
+  "/api/healthz",
+];
+
+/** Optimistic (cookie-only) check - centralizes redirect logic per the Next.js Proxy guidance.
+ * Every Route Handler also calls `requireAuth()` itself as the real, defense-in-depth check. */
+export async function proxy(request: NextRequest) {
+  const { config } = getConfig();
+  if (!config.auth.enabled) return NextResponse.next();
+
+  const { pathname } = request.nextUrl;
+  if (
+    PUBLIC_PATHS.some(
+      (path) => pathname === path || pathname.startsWith("/_next"),
+    )
+  ) {
+    return NextResponse.next();
+  }
+
+  const isApiRoute = pathname.startsWith("/api/");
+
+  if (isApiRoute) {
+    // Token-authed API clients won't have a session cookie; let the route handler's requireAuth()
+    // do the real check instead of rejecting here.
+    if (request.headers.get("authorization")?.startsWith("Bearer "))
+      return NextResponse.next();
+  }
+
+  const sealed = request.cookies.get("triggershell_session")?.value;
+  const session = await verifySessionCookieValue(sealed);
+
+  if (!session?.userId) {
+    if (isApiRoute) {
+      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+    }
+    const loginUrl = new URL("/login", request.url);
+    loginUrl.searchParams.set("next", pathname);
+    return NextResponse.redirect(loginUrl);
+  }
+
+  return NextResponse.next();
+}
+
+export const config = {
+  matcher: ["/((?!_next/static|_next/image|favicon.ico).*)"],
+};