docs: reconcile docs with code across last 3 releases (#54254)

Audited the last 3 releases (v2026.5.28..main) against the docs site and
fixed code-vs-docs drift:

- slash-commands: add /moa, /prompt, /pet, /hatch, /timestamps
- cli-commands: add hermes pets / project / desktop / whatsapp-cloud +
  dashboard register; correct --insecure (now a deprecated no-op);
  add gateway migrate-legacy + enroll --wake-url + dashboard --skip-build
- environment-variables: document the remaining ~48 env vars (SimpleX,
  Photon, Teams adapter, per-platform *_ALLOW_ALL_USERS, home-channel vars,
  IRC, Brave/Krea/Notion/Linear/Airtable/Tenor keys, QQ_SANDBOX) — full
  OPTIONAL_ENV_VARS (265) now covered
- configuration: document tool_loop_guardrails, goals, prompt_caching,
  network, onboarding, dashboard config blocks
- toolsets/tools-reference + tools.md: add coding/project toolsets and
  read_terminal/project_* tools; remove the stale messaging toolset and
  send_message agent tool (removed in #47856); drop stale RL-training prose
- messaging: new IRC channel page (adapter shipped without docs) + index
  row + sidebar + env vars
- pets: document the /hatch AI generation pipeline + Nous/OpenRouter image
  backend
- web-dashboard: document the bearer-token / TokenPrincipal service auth path
- purge agent-callable send_message references across guides/features and
  the research-paper-writing skill (tool removed in #47856)

Verified: docusaurus build succeeds; all authored internal links resolve.

website/docs/developer-guide/adding-platform-adapters.md

@@ -185,7 +185,7 @@ When you call `ctx.register_platform()`, the following integration points are ha
 | YAML config bridge | `apply_yaml_config_fn` translates `config.yaml` keys into env vars / extras |
 | Cron delivery | `cron_deliver_env_var` makes `deliver=<name>` work |
 | `hermes config` UI entries | `requires_env` / `optional_env` in `plugin.yaml` auto-populate |
-| send_message tool | Routes through live gateway adapter |
+| send engine (`tools/send_message_tool.py`) | Routes through live gateway adapter |
 | Webhook cross-platform delivery | Registry checked for known platforms |
 | `/update` command access | `allow_update_command` flag |
 | Channel directory | Plugin platforms included in enumeration |