docs: fix stale and incorrect documentation across 18 files

Cross-referenced all 84 docs pages against the actual codebase and
corrected every discrepancy found.

Reference docs:
- faq.md: Fix non-existent commands (/stats→/usage, /context→/usage,
  hermes models→hermes model, hermes config get→hermes config show,
  hermes gateway logs→cat gateway.log, async→sync chat() call)
- cli-commands.md: Fix --provider choices list (remove providers not
  in argparse), add undocumented -s/--skills flag
- slash-commands.md: Add missing /queue and /resume commands, fix
  /approve args_hint to show [session|always]
- tools-reference.md: Remove duplicate vision and web toolset sections
- environment-variables.md: Fix HERMES_INFERENCE_PROVIDER list (add
  copilot-acp, remove alibaba to match actual argparse choices)

Configuration & user guide:
- configuration.md: Fix approval_mode→approvals.mode (manual not ask),
  checkpoints.enabled default true not false, human_delay defaults
  (500/2000→800/2500), remove non-existent delegation.max_iterations
  and delegation.default_toolsets, fix website_blocklist nesting
  under security:, add .hermes.md and CLAUDE.md to context files
  table with priority system explanation
- security.md: Fix website_blocklist nesting under security:
- context-files.md: Add .hermes.md/HERMES.md and CLAUDE.md support,
  document priority-based first-match-wins loading behavior
- cli.md: Fix personalities config nesting (top-level, not under agent:)
- delegation.md: Fix model override docs (config-level, not per-call
  tool parameter)
- rl-training.md: Fix log directory (tinker-atropos/logs/→
  ~/.hermes/logs/rl_training/)
- tts.md: Fix Discord delivery format (voice bubble with fallback,
  not just file attachment)
- git-worktrees.md: Remove outdated v0.2.0 version reference

Developer guide:
- prompt-assembly.md: Add .hermes.md, CLAUDE.md, document priority
  system for context files
- agent-loop.md: Fix callback list (remove non-existent
  message_callback, add stream_delta_callback, tool_gen_callback,
  status_callback)

Messaging & guides:
- webhooks.md: Fix command (hermes setup gateway→hermes gateway setup)
- tips.md: Fix session idle timeout (120min→24h), config file
  (gateway.json→config.yaml)
- build-a-hermes-plugin.md: Fix plugin.yaml provides: format
  (provides_tools/provides_hooks as lists), note register_command()
  as not yet implemented

website/docs/user-guide/features/delegation.md

@@ -131,15 +131,13 @@ Single-task delegation runs directly without thread pool overhead.
 
 ## Model Override
 
-You can use a different model for subagents — useful for delegating simple tasks to cheaper/faster models:
+You can configure a different model for subagents via `config.yaml` — useful for delegating simple tasks to cheaper/faster models:
 
-```python
-delegate_task(
-    goal="Summarize this README file",
-    context="File at /project/README.md",
-    toolsets=["file"],
-    model="google/gemini-flash-2.0"  # Cheaper model for simple tasks
-)
+```yaml
+# In ~/.hermes/config.yaml
+delegation:
+  model: "google/gemini-flash-2.0"    # Cheaper model for subagents
+  provider: "openrouter"              # Optional: route subagents to a different provider
 ```
 
 If omitted, subagents use the same model as the parent.