Replace the Python CLI with a Node CLI, add a systemd service command

The app is already 100% Node, so the Python launcher was pure overhead - it
existed mainly to bootstrap Node, which is circular. The CLI is now merged
into app/ (the single published npm package): `triggershell start` validates
the config and imports server.ts directly in-process, so server.ts's own
SIGTERM/SIGINT handling just works with no signal-relay/child-process layer
needed. `dev` is dropped from the public CLI (contributors use `pnpm --dir
app dev` directly); there's no `build` command either, since the package
ships a prebuilt `.next` via a `prepack` hook. Adds `triggershell service
install|uninstall|status` for running as a per-user or system systemd unit.

Also fixes two bugs found while wiring this up: server.ts resolved `.next`
relative to `process.cwd()`, which broke once the CLI could run from a
directory other than the app itself; and an explicitly-`files`-listed
package directory bypasses .npmignore for its subpaths, so `.next/cache`
was inflating the npm tarball to ~670MB (now stripped in `prepack`, ~7MB).

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

app/server.ts

@@ -1,5 +1,7 @@
 import "./src/bootstrap/async-local-storage-polyfill";
 import { createServer } from "node:http";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
 import next from "next";
 import { WebSocketServer } from "ws";
 import { getConfig } from "./src/lib/config/load";
@@ -19,7 +21,10 @@ migrateOnBoot();
 syncAuthFromConfig();
 reconcileOrphanedRuns();
 
-const app = next({ dev, hostname, port });
+// `dir` must be this file's own directory, not `process.cwd()` - when launched by the installed
+// `triggershell` CLI, the working directory is wherever the user's config lives, not the package.
+const dir = path.dirname(fileURLToPath(import.meta.url));
+const app = next({ dev, dir, hostname, port });
 const handle = app.getRequestHandler();
 
 app.prepare().then(() => {