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/enhanced-resolve/lib/MainFieldPlugin.js

@@ -0,0 +1,97 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const DescriptionFileUtils = require("./DescriptionFileUtils");
+
+/** @typedef {import("./Resolver")} Resolver */
+/** @typedef {import("./Resolver").JsonObject} JsonObject */
+/** @typedef {import("./Resolver").ResolveRequest} ResolveRequest */
+/** @typedef {import("./Resolver").ResolveStepHook} ResolveStepHook */
+
+/** @typedef {{ name: string | string[], forceRelative: boolean }} MainFieldOptions */
+
+const alreadyTriedMainField = Symbol("alreadyTriedMainField");
+
+// Sentinel cached for description files where the main field resolves to a
+// value we cannot use (missing, non-string, ".", "./"). Cheaper to store and
+// check than to re-walk the description file on every resolve.
+const NO_MAIN = Symbol("NoMain");
+
+module.exports = class MainFieldPlugin {
+	/**
+	 * @param {string | ResolveStepHook} source source
+	 * @param {MainFieldOptions} options options
+	 * @param {string | ResolveStepHook} target target
+	 */
+	constructor(source, options, target) {
+		this.source = source;
+		this.options = options;
+		this.target = target;
+		// Cache the resolved `mainModule` per description-file content. The
+		// options (`name`, `forceRelative`) are fixed for this plugin
+		// instance, so caching against content alone is safe. Stores either
+		// the ready-to-use request string or the `NO_MAIN` sentinel.
+		/** @type {WeakMap<JsonObject, string | typeof NO_MAIN>} */
+		this._mainModuleCache = new WeakMap();
+	}
+
+	/**
+	 * @param {Resolver} resolver the resolver
+	 * @returns {void}
+	 */
+	apply(resolver) {
+		const target = resolver.ensureHook(this.target);
+		resolver
+			.getHook(this.source)
+			.tapAsync("MainFieldPlugin", (request, resolveContext, callback) => {
+				if (
+					request.path !== request.descriptionFileRoot ||
+					/** @type {ResolveRequest & { [alreadyTriedMainField]?: string }} */
+					(request)[alreadyTriedMainField] === request.descriptionFilePath ||
+					!request.descriptionFilePath
+				) {
+					return callback();
+				}
+				const descFileData = /** @type {JsonObject} */ (
+					request.descriptionFileData
+				);
+				let mainModule = this._mainModuleCache.get(descFileData);
+				if (mainModule === undefined) {
+					let raw =
+						/** @type {string | null | undefined} */
+						(DescriptionFileUtils.getField(descFileData, this.options.name));
+					if (!raw || typeof raw !== "string" || raw === "." || raw === "./") {
+						this._mainModuleCache.set(descFileData, NO_MAIN);
+						return callback();
+					}
+					if (this.options.forceRelative && !/^\.\.?\//.test(raw)) {
+						raw = `./${raw}`;
+					}
+					mainModule = raw;
+					this._mainModuleCache.set(descFileData, mainModule);
+				} else if (mainModule === NO_MAIN) {
+					return callback();
+				}
+				const filename = resolver.basename(request.descriptionFilePath);
+				/** @type {ResolveRequest & { [alreadyTriedMainField]?: string }} */
+				const obj = {
+					...request,
+					request: mainModule,
+					module: false,
+					directory: mainModule.endsWith("/"),
+					[alreadyTriedMainField]: request.descriptionFilePath,
+				};
+				return resolver.doResolve(
+					target,
+					obj,
+					`use ${mainModule} from ${this.options.name} in ${filename}`,
+					resolveContext,
+					callback,
+				);
+			});
+	}
+};