feat: default list_alerts to active alerts only

Change list_alerts (MCP tool) and alerts (CLI command) to show only
active (non-silenced, non-inhibited) alerts by default. Add state=all
option and --all CLI flag to show all alerts when needed.

- MCP: list_alerts with no state param now returns active alerts only
- MCP: list_alerts with state=all returns all alerts (previous default)
- CLI: alerts command defaults to active, --all shows everything
- Add tests for new default behavior and state=all option
- Update README with new CLI examples
- Bump version to 0.3.0
- Clarify version bumping rules in CLAUDE.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/monitoring/handlers.go

@@ -91,8 +91,8 @@ func listAlertsTool() mcp.Tool {
 			Properties: map[string]mcp.Property{
 				"state": {
 					Type:        "string",
-					Description: "Filter by alert state: 'active', 'suppressed', or 'unprocessed'",
-					Enum:        []string{"active", "suppressed", "unprocessed"},
+					Description: "Filter by alert state: 'active', 'suppressed', 'unprocessed', or 'all' (default: active)",
+					Enum:        []string{"active", "suppressed", "unprocessed", "all"},
 				},
 				"severity": {
 					Type:        "string",
@@ -236,22 +236,24 @@ func makeListAlertsHandler(am *AlertmanagerClient) mcp.ToolHandler {
 	return func(ctx context.Context, args map[string]interface{}) (mcp.CallToolResult, error) {
 		filters := AlertFilters{}
 
-		if state, ok := args["state"].(string); ok && state != "" {
-			switch state {
-			case "active":
-				active := true
-				filters.Active = &active
-				silenced := false
-				filters.Silenced = &silenced
-				inhibited := false
-				filters.Inhibited = &inhibited
-			case "suppressed":
-				active := false
-				filters.Active = &active
-			case "unprocessed":
-				unprocessed := true
-				filters.Unprocessed = &unprocessed
-			}
+		state, _ := args["state"].(string)
+		switch state {
+		case "active", "":
+			// Default to active alerts only (non-silenced, non-inhibited)
+			active := true
+			filters.Active = &active
+			silenced := false
+			filters.Silenced = &silenced
+			inhibited := false
+			filters.Inhibited = &inhibited
+		case "suppressed":
+			active := false
+			filters.Active = &active
+		case "unprocessed":
+			unprocessed := true
+			filters.Unprocessed = &unprocessed
+		case "all":
+			// No filters - return everything
 		}
 
 		if severity, ok := args["severity"].(string); ok && severity != "" {