docs: fix 40+ discrepancies between documentation and codebase (#5818)

Comprehensive audit of all ~100 doc pages against the actual code, fixing:

Reference docs:
- HERMES_API_TIMEOUT default 900 -> 1800 (env-vars)
- TERMINAL_DOCKER_IMAGE default python:3.11 -> nikolaik/python-nodejs (env-vars)
- compression.summary_model default shown as gemini -> actually empty string (env-vars)
- Add missing GOOGLE_API_KEY, GEMINI_API_KEY, GEMINI_BASE_URL env vars (env-vars)
- Add missing /branch (/fork) slash command (slash-commands)
- Fix hermes-cli tool count 39 -> 38 (toolsets-reference)
- Fix hermes-api-server drop list to include text_to_speech (toolsets-reference)
- Fix total tool count 47 -> 48, standalone 14 -> 15 (tools-reference)

User guide:
- web_extract.timeout default 30 -> 360 (configuration)
- Remove display.theme_mode (not implemented in code) (configuration)
- Remove display.background_process_notifications (not in defaults) (configuration)
- Browser inactivity timeout 300/5min -> 120/2min (browser)
- Screenshot path browser_screenshots -> cache/screenshots (browser)
- batch_runner default model claude-sonnet-4-20250514 -> claude-sonnet-4.6
- Add minimax to TTS provider list (voice-mode)
- Remove credential_pool_strategies from auth.json example (credential-pools)
- Fix Slack token path platforms/slack/ -> root ~/.hermes/ (slack)
- Fix Matrix store path for new installs (matrix)
- Fix WhatsApp session path for new installs (whatsapp)
- Fix HomeAssistant config from gateway.json to config.yaml (homeassistant)
- Fix WeCom gateway start command (wecom)

Developer guide:
- Fix tool/toolset counts in architecture overview
- Update line counts: main.py ~5500, setup.py ~3100, run.py ~7500, mcp_tool ~2200
- Replace nonexistent agent/memory_store.py with memory_manager.py + memory_provider.py
- Update _discover_tools() list: remove honcho_tools, add skill_manager_tool
- Add session_search and delegate_task to intercepted tools list (agent-loop)
- Fix budget warning: two-tier system (70% caution, 90% warning) (agent-loop)
- Fix gateway auth order (per-platform first, global last) (gateway-internals)
- Fix email_adapter.py -> email.py, add webhook.py + api_server.py (gateway-internals)
- Add 7 missing providers to provider-runtime list

Other:
- Add Docker --cap-add entries to security doc
- Fix Python version 3.10+ -> 3.11+ (contributing)
- Fix AGENTS.md discovery claim (not hierarchical walk) (tips)
- Fix cron 'add' -> canonical 'create' (cron-internals)
- Add pre_api_request/post_api_request hooks to plugin guide
- Add Google/Gemini provider to providers page
- Clarify OPENAI_BASE_URL deprecation (providers)

website/docs/reference/slash-commands.md

@@ -37,6 +37,7 @@ Type `/` in the CLI to open the autocomplete menu. Built-in commands are case-in
 | `/background <prompt>` (alias: `/bg`) | Run a prompt in a separate background session. The agent processes your prompt independently — your current session stays free for other work. Results appear as a panel when the task finishes. See [CLI Background Sessions](/docs/user-guide/cli#background-sessions). |
 | `/btw <question>` | Ephemeral side question using session context (no tools, not persisted). Useful for quick clarifications without affecting the conversation history. |
 | `/plan [request]` | Load the bundled `plan` skill to write a markdown plan instead of executing the work. Plans are saved under `.hermes/plans/` relative to the active workspace/backend working directory. |
+| `/branch [name]` (alias: `/fork`) | Branch the current session (explore a different path) |
 
 ### Configuration