refactor: enhance user context handling and update template mappings

backend/templates/BOARD_TOOLS.md.j2

@@ -1,16 +1,23 @@
-# TOOLS.md
+{% set is_main = (is_main_agent | default(false) | string | lower) in ["true", "1", "yes"] %}
 {% set is_lead = (is_board_lead | default(false) | string | lower) in ["true", "1", "yes"] %}
+# TOOLS.md
 
 - `BASE_URL={{ base_url }}`
 - `AUTH_TOKEN={{ auth_token }}`
 - `AGENT_NAME={{ agent_name }}`
 - `AGENT_ID={{ agent_id }}`
+{% if board_id is defined %}
 - `BOARD_ID={{ board_id }}`
+{% endif %}
 - `WORKSPACE_ROOT={{ workspace_root }}`
+{% if workspace_path is defined %}
 - `WORKSPACE_PATH={{ workspace_path }}`
+{% endif %}
 - Required tools: `curl`, `jq`
 
-{% if is_lead %}
+{% if is_main %}
+{% set role_tag = "agent-main" %}
+{% elif is_lead %}
 {% set role_tag = "agent-lead" %}
 {% else %}
 {% set role_tag = "agent-worker" %}