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/app/(app)/docs/page.tsx

@@ -0,0 +1,35 @@
+export const dynamic = "force-dynamic";
+
+import type { Metadata } from "next";
+import Link from "next/link";
+import { BookOpen, ChevronRight } from "lucide-react";
+import { DOCS } from "@/lib/docs";
+import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
+
+export const metadata: Metadata = { title: "Docs" };
+
+export default function DocsIndexPage() {
+  return (
+    <div className="flex flex-col gap-4">
+      <h1 className="text-2xl font-semibold tracking-tight">Docs</h1>
+      <div className="grid gap-3 sm:grid-cols-2">
+        {DOCS.map((doc) => (
+          <Link key={doc.slug} href={`/docs/${doc.slug}`}>
+            <Card className="hover:border-foreground/30 h-full transition-colors">
+              <CardHeader className="flex flex-row items-start justify-between gap-2 space-y-0">
+                <div className="flex items-center gap-2">
+                  <BookOpen className="text-muted-foreground size-4.5 shrink-0" />
+                  <CardTitle className="text-base">{doc.title}</CardTitle>
+                </div>
+                <ChevronRight className="text-muted-foreground size-4 shrink-0" />
+              </CardHeader>
+              <CardContent className="text-muted-foreground text-sm">
+                {doc.description}
+              </CardContent>
+            </Card>
+          </Link>
+        ))}
+      </div>
+    </div>
+  );
+}