feat: Phase 1 — extract the client (web SPA + desktop) to dtoro/oikos-web

Problem: the hexagonal refactor churns the backend tree for nine more
phases; the UI delivery stack (web/ SPA, cmd/desktop Wails wrapper,
compose/web image) must move to its own repo first so doc/layout
rewrites land once on a backend-only tree.

Change:
- New repo git.hubris.network/dtoro/oikos-web (v0.33.0): web/, desktop/
  (updateURL repointed to oikos-web releases), compose/, own CI (web +
  desktop jobs), own deploy script (CI-green gate, TOCTOU guard,
  version-tagged images, prune-to-3), own webhook receiver on :9798 +
  launchd unit, own compose project publishing the same 8091:80.
- Cutover executed on mac-mini in order: oikos stack's web service
  stopped+removed, oikos-web project brought up on 8091; outer Caddy
  untouched (targets the published port) — serving + Authentik flow +
  /wails 404 quirk verified post-cutover.
- Stripped from oikos: web/, cmd/desktop/, compose/web/, desktop CI
  workflow, ci.yml web job, Makefile ui/desktop/desktop-package/install
  targets, the compose web service, oikos-web from deploy.sh's fallback
  prune list; wails + go-keyring dropped from go.mod, vendor synced.
- README / CONTRIBUTING / AGENTS.md / .agents dev+operations docs now
  point at the new repo; mbse + mascot design docs carry a path note.

Risk: production SPA serving depends on the new pipeline now; rollback
is versioned-image re-up of the old web service from a pre-split
checkout (port 8091). Desktop builds installed before the split still
check dtoro/oikos releases — one manual reinstall, noted in the
oikos-web release notes.

Verification: go vet, make test (race), make generate-check, golangci
(no new findings; baseline down 400→365); post-cutover curls —
localhost:8091 200, /wails/runtime.js 404, outer Caddy 302 Authentik.

web/node_modules/path-key/index.d.ts

@@ -0,0 +1,40 @@
+/// <reference types="node" />
+
+declare namespace pathKey {
+	interface Options {
+		/**
+		Use a custom environment variables object. Default: [`process.env`](https://nodejs.org/api/process.html#process_process_env).
+		*/
+		readonly env?: {[key: string]: string | undefined};
+
+		/**
+		Get the PATH key for a specific platform. Default: [`process.platform`](https://nodejs.org/api/process.html#process_process_platform).
+		*/
+		readonly platform?: NodeJS.Platform;
+	}
+}
+
+declare const pathKey: {
+	/**
+	Get the [PATH](https://en.wikipedia.org/wiki/PATH_(variable)) environment variable key cross-platform.
+
+	@example
+	```
+	import pathKey = require('path-key');
+
+	const key = pathKey();
+	//=> 'PATH'
+
+	const PATH = process.env[key];
+	//=> '/usr/local/bin:/usr/bin:/bin'
+	```
+	*/
+	(options?: pathKey.Options): string;
+
+	// TODO: Remove this for the next major release, refactor the whole definition to:
+	// declare function pathKey(options?: pathKey.Options): string;
+	// export = pathKey;
+	default: typeof pathKey;
+};
+
+export = pathKey;