Vendor Chatwoot Vue 3 frontend into frontend/

Copy the Chatwoot (v4.14.0) frontend runnable subset into frontend/ for
customization:
- app/javascript/ (Vue SPA: dashboard, widget, sdk, portal, superadmin)
- app/views/ (ERB templates for vite-plugin-ruby entrypoint resolution)
- app/helpers/, app/assets/ (Rails view helpers, static assets)
- enterprise/ (Enterprise edition frontend overlay)
- config/vite.json, vite.config.ts, bin/vite (Vite-Rails toolchain)
- package.json, pnpm-lock.yaml, tailwind/postcss/eslint configs
- Gemfile, Gemfile.lock (vite_rails gem for bin/vite binstub)

Excluded Rails backend: controllers, models, services, jobs, mailers,
policies, db, lib, spec, public, node_modules.

Update references to the new frontend location:
- .gitignore: exclude frontend build artifacts (node_modules, tmp, packs),
  keep frontend/bin/ and frontend/vendor/ via negation
- backend/scripts/parity_frontend_smoke.sh: CHATWOOT_DIR default
  reference/chatwoot -> ../frontend
- backend/scripts/parity_frontend_browser_smoke.mjs: same default update
- AGENTS.md: add frontend section with Rails/Vite coupling notes
- README: architecture tree includes frontend/

backend/scripts/parity_frontend_browser_smoke.mjs

@@ -6,7 +6,7 @@ import { tmpdir } from 'node:os';
 import path from 'node:path';
 
 const root = process.env.GOCHAT_ROOT || process.cwd();
-const chatwootDir = process.env.CHATWOOT_DIR || path.join(root, 'reference/chatwoot');
+const chatwootDir = process.env.CHATWOOT_DIR || path.join(root, 'frontend');
 const logDir = process.env.GOCHAT_SMOKE_LOG_DIR || path.join(root, '.tmp/frontend-smoke');
 const apiHost = process.env.GOCHAT_SMOKE_API_HOST || '127.0.0.1';
 const apiPort = process.env.GOCHAT_SMOKE_API_PORT || '3000';

backend/scripts/parity_frontend_smoke.sh

@@ -4,7 +4,7 @@
 set -euo pipefail
 
 ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
-CHATWOOT_DIR="${CHATWOOT_DIR:-$ROOT/reference/chatwoot}"
+CHATWOOT_DIR="${CHATWOOT_DIR:-$ROOT/../frontend}"
 LOG_DIR="${GOCHAT_SMOKE_LOG_DIR:-$ROOT/.tmp/frontend-smoke}"
 REPORT_PATH="${GOCHAT_SMOKE_REPORT:-$ROOT/docs/parity/frontend_smoke_report.md}"
 API_HOST="${GOCHAT_SMOKE_API_HOST:-127.0.0.1}"
@@ -33,7 +33,7 @@ Modes:
   --no-seed    Skip seed during --api-smoke and use GOCHAT_SEED_* values already present in DB.
 
 Environment:
-  CHATWOOT_DIR                  Chatwoot checkout path. Default: reference/chatwoot
+  CHATWOOT_DIR                  Chatwoot checkout path. Default: ../frontend (repo root frontend/)
   GOCHAT_SMOKE_API_PORT         GoChat backend port. Default: 3000
   GOCHAT_SMOKE_FRONTEND_HOST    Vite frontend host. Default: localhost
   GOCHAT_SMOKE_FRONTEND_PORT    Vite frontend port. Default: 3036