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/cross-spawn/lib/enoent.js

@@ -0,0 +1,59 @@
+'use strict';
+
+const isWin = process.platform === 'win32';
+
+function notFoundError(original, syscall) {
+    return Object.assign(new Error(`${syscall} ${original.command} ENOENT`), {
+        code: 'ENOENT',
+        errno: 'ENOENT',
+        syscall: `${syscall} ${original.command}`,
+        path: original.command,
+        spawnargs: original.args,
+    });
+}
+
+function hookChildProcess(cp, parsed) {
+    if (!isWin) {
+        return;
+    }
+
+    const originalEmit = cp.emit;
+
+    cp.emit = function (name, arg1) {
+        // If emitting "exit" event and exit code is 1, we need to check if
+        // the command exists and emit an "error" instead
+        // See https://github.com/IndigoUnited/node-cross-spawn/issues/16
+        if (name === 'exit') {
+            const err = verifyENOENT(arg1, parsed);
+
+            if (err) {
+                return originalEmit.call(cp, 'error', err);
+            }
+        }
+
+        return originalEmit.apply(cp, arguments); // eslint-disable-line prefer-rest-params
+    };
+}
+
+function verifyENOENT(status, parsed) {
+    if (isWin && status === 1 && !parsed.file) {
+        return notFoundError(parsed.original, 'spawn');
+    }
+
+    return null;
+}
+
+function verifyENOENTSync(status, parsed) {
+    if (isWin && status === 1 && !parsed.file) {
+        return notFoundError(parsed.original, 'spawnSync');
+    }
+
+    return null;
+}
+
+module.exports = {
+    hookChildProcess,
+    verifyENOENT,
+    verifyENOENTSync,
+    notFoundError,
+};