docs: fill documentation gaps from recent PRs (#2183)

- slash-commands.md: add /approve, /deny (gateway-only), /statusbar
  (CLI-only); update Notes section with new platform-specific commands
- messaging/index.md: add Webhooks to architecture diagram, platform
  toolsets table, and Next Steps links; add /approve and /deny to
  Chat Commands table
- environment-variables.md: add HONCHO_BASE_URL for self-hosted
  Honcho instances
- configuration.md: add Context Pressure Warnings section (separate
  from iteration budget pressure); add base_url to OpenAI TTS config;
  add display.show_cost to Display Settings
- tts.md: add base_url to OpenAI TTS config example

Co-authored-by: Test <test@test.com>

website/docs/reference/environment-variables.md

@@ -92,6 +92,7 @@ For native Anthropic auth, Hermes prefers Claude Code's own credential files whe
 | `STT_OPENAI_BASE_URL` | Override the OpenAI-compatible STT endpoint |
 | `GITHUB_TOKEN` | GitHub token for Skills Hub (higher API rate limits, skill publish) |
 | `HONCHO_API_KEY` | Cross-session user modeling ([honcho.dev](https://honcho.dev/)) |
+| `HONCHO_BASE_URL` | Base URL for self-hosted Honcho instances (default: Honcho cloud). No API key required for local instances |
 | `TINKER_API_KEY` | RL training ([tinker-console.thinkingmachines.ai](https://tinker-console.thinkingmachines.ai/)) |
 | `WANDB_API_KEY` | RL training metrics ([wandb.ai](https://wandb.ai/)) |
 | `DAYTONA_API_KEY` | Daytona cloud sandboxes ([daytona.io](https://daytona.io/)) |