fix: wire toolHintMaxLength through AgentLoop constructors

The config field was added but never passed from config to AgentLoop.
The value was always falling back to the default (40) regardless of
what was set in config.json.

Now passes tool_hint_max_length through all AgentLoop() call sites:
- nanobot/nanobot.py (main bot)
- nanobot/cli/commands.py (CLI agent, dev, webui commands)

Also adds documentation in docs/configuration.md.

nanobot/cli/commands.py

@@ -557,6 +557,7 @@ def serve(
         context_block_limit=runtime_config.agents.defaults.context_block_limit,
         max_tool_result_chars=runtime_config.agents.defaults.max_tool_result_chars,
         provider_retry_mode=runtime_config.agents.defaults.provider_retry_mode,
+        tool_hint_max_length=runtime_config.agents.defaults.tool_hint_max_length,
         web_config=runtime_config.tools.web,
         exec_config=runtime_config.tools.exec,
         restrict_to_workspace=runtime_config.tools.restrict_to_workspace,
@@ -681,6 +682,7 @@ def _run_gateway(
         context_block_limit=config.agents.defaults.context_block_limit,
         max_tool_result_chars=config.agents.defaults.max_tool_result_chars,
         provider_retry_mode=config.agents.defaults.provider_retry_mode,
+        tool_hint_max_length=config.agents.defaults.tool_hint_max_length,
         exec_config=config.tools.exec,
         cron_service=cron,
         restrict_to_workspace=config.tools.restrict_to_workspace,
@@ -1073,6 +1075,7 @@ def agent(
         context_block_limit=config.agents.defaults.context_block_limit,
         max_tool_result_chars=config.agents.defaults.max_tool_result_chars,
         provider_retry_mode=config.agents.defaults.provider_retry_mode,
+        tool_hint_max_length=config.agents.defaults.tool_hint_max_length,
         exec_config=config.tools.exec,
         cron_service=cron,
         restrict_to_workspace=config.tools.restrict_to_workspace,