feat: add profiles — run multiple isolated Hermes instances (#3681)

Each profile is a fully independent HERMES_HOME with its own config,
API keys, memory, sessions, skills, gateway, cron, and state.db.

Core module: hermes_cli/profiles.py (~900 lines)
  - Profile CRUD: create, delete, list, show, rename
  - Three clone levels: blank, --clone (config), --clone-all (everything)
  - Export/import: tar.gz archive for backup and migration
  - Wrapper alias scripts (~/.local/bin/<name>)
  - Collision detection for alias names
  - Sticky default via ~/.hermes/active_profile
  - Skill seeding via subprocess (handles module-level caching)
  - Auto-stop gateway on delete with disable-before-stop for services
  - Tab completion generation for bash and zsh

CLI integration (hermes_cli/main.py):
  - _apply_profile_override(): pre-import -p/--profile flag + sticky default
  - Full 'hermes profile' subcommand: list, use, create, delete, show,
    alias, rename, export, import
  - 'hermes completion bash/zsh' command
  - Multi-profile skill sync in hermes update

Display (cli.py, banner.py, gateway/run.py):
  - CLI prompt: 'coder ❯' when using a non-default profile
  - Banner shows profile name
  - Gateway startup log includes profile name

Gateway safety:
  - Token locks: Discord, Slack, WhatsApp, Signal (extends Telegram pattern)
  - Port conflict detection: API server, webhook adapter

Diagnostics (hermes_cli/doctor.py):
  - Profile health section: lists profiles, checks config, .env, aliases
  - Orphan alias detection: warns when wrapper points to deleted profile

Tests (tests/hermes_cli/test_profiles.py):
  - 71 automated tests covering: validation, CRUD, clone levels, rename,
    export/import, active profile, isolation, alias collision, completion
  - Full suite: 6760 passed, 0 new failures

Documentation:
  - website/docs/user-guide/profiles.md: full user guide (12 sections)
  - website/docs/reference/profile-commands.md: command reference (12 commands)
  - website/docs/reference/faq.md: 6 profile FAQ entries
  - website/sidebars.ts: navigation updated

gateway/platforms/webhook.py

@@ -118,6 +118,17 @@ class WebhookAdapter(BasePlatformAdapter):
         app.router.add_get("/health", self._handle_health)
         app.router.add_post("/webhooks/{route_name}", self._handle_webhook)
 
+        # Port conflict detection — fail fast if port is already in use
+        import socket as _socket
+        try:
+            with _socket.socket(_socket.AF_INET, _socket.SOCK_STREAM) as _s:
+                _s.settimeout(1)
+                _s.connect(('127.0.0.1', self._port))
+            logger.error('[webhook] Port %d already in use. Set a different port in config.yaml: platforms.webhook.port', self._port)
+            return False
+        except (ConnectionRefusedError, OSError):
+            pass  # port is free
+
         self._runner = web.AppRunner(app)
         await self._runner.setup()
         site = web.TCPSite(self._runner, self._host, self._port)