fix: session ID collision in cmd_start by excluding pm_agent_session_id

When cmd_start forks a new session, the session detection logic now
excludes both base_session_id AND pm_agent_session_id to prevent
forked sessions from being misidentified as the pm-agent session.

This addresses issue #81 where forked sessions were showing the same
session ID as the pm-agent.

skills/kugetsu/SKILL.md

@@ -27,6 +27,27 @@ cp skills/kugetsu/scripts/kugetsu ~/.local/bin/kugetsu
 chmod +x ~/.local/bin/kugetsu
 ```
 
+## Configuration
+
+User overrides can be set in `~/.kugetsu/config`. This file is sourced on each kugetsu command call, so changes take effect immediately without re-initialization.
+
+A default config file is created during `kugetsu init` with commented examples:
+
+```bash
+# User configuration overrides
+# Values set here take precedence over defaults
+# Changes take effect immediately (no re-init needed)
+
+# Max concurrent dev agents (default: 3)
+# MAX_CONCURRENT_AGENTS=5
+```
+
+### Available Config Options
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `MAX_CONCURRENT_AGENTS` | 3 | Maximum number of concurrent dev agents |
+
 ## Architecture
 
 ### Session Pattern

skills/kugetsu/scripts/kugetsu

@@ -10,6 +10,11 @@ NOTIFICATIONS_FILE="$KUGETSU_DIR/notifications.json"
 LOGS_DIR="$KUGETSU_DIR/logs"
 MAX_CONCURRENT_AGENTS="${MAX_CONCURRENT_AGENTS:-3}"
 
+# Load user config overrides (~/.kugetsu/config)
+if [ -f "$KUGETSU_DIR/config" ]; then
+    source "$KUGETSU_DIR/config"
+fi
+
 count_active_dev_sessions() {
     local count=0
     if [ -d "$SESSIONS_DIR" ]; then
@@ -681,6 +686,18 @@ cmd_init() {
 
     ensure_dirs
 
+    if [ ! -f "$KUGETSU_DIR/config" ]; then
+        cat > "$KUGETSU_DIR/config" << 'EOF'
+# User configuration overrides
+# Values set here take precedence over defaults
+# Changes take effect immediately (no re-init needed)
+
+# Max concurrent dev agents (default: 3)
+# MAX_CONCURRENT_AGENTS=5
+EOF
+        echo "Created config file: $KUGETSU_DIR/config"
+    fi
+
     local existing_base=$(get_base_session_id)
     local existing_pm=$(get_pm_agent_session_id)
     
@@ -835,7 +852,7 @@ cmd_start() {
     local after_sessions=$(opencode session list 2>/dev/null | grep -oP '^ses_\w+' | sort)
     local new_session_id=""
     while IFS= read -r sess; do
-        if [[ ! "$before_set" =~ \|${sess}\| ]] && [[ "$sess" != "$base_session_id" ]]; then
+        if [[ ! "$before_set" =~ \|${sess}\| ]] && [[ "$sess" != "$base_session_id" ]] && [[ "$sess" != "$pm_agent_session_id" ]]; then
             new_session_id="$sess"
             break
         fi