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/bootstrap/async-local-storage-polyfill.ts

@@ -0,0 +1,9 @@
+import { AsyncLocalStorage } from "node:async_hooks";
+
+// Next's App Router needs this global set up before its own modules evaluate. `next start`/`next dev`
+// do this via their CLI bootstrap; the programmatic `next()` API used by our custom server does not.
+// Must be the first import in server.ts - ESM import evaluation order (not textual position) is what
+// guarantees this runs before the `next` package's module graph does.
+if (typeof globalThis.AsyncLocalStorage !== "function") {
+  globalThis.AsyncLocalStorage = AsyncLocalStorage;
+}