feat(scheduling): node tags + service placement_tags affinity (#58)

Operator-set node labels (node_agents.tags) gate which nodes a service
may schedule onto: services.placement_tags requires every listed tag.
auto and spread filter eligible agents by tags; tags are re-evaluated
each reconcile so retagging a node re-spreads replicas. Pin + tags and
local + tags rejected; empty array clears the requirement.

Surfaces: --placement-tags on services create/update, nodes update
--tags, MCP args, OpenAPI, node-detail tag editor, service-detail
placement-tags input.

Generated with [Devin](https://devin.ai)

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/cli/commands/nodes.go

@@ -2,6 +2,7 @@ package commands
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/spf13/cobra"
 )
@@ -83,7 +84,7 @@ var nodesDeleteCmd = &cobra.Command{
 
 var nodesUpdateCmd = &cobra.Command{
 	Use:   "update <id>",
-	Short: "Update a node agent (--name, --auto-prune)",
+	Short: "Update a node agent (--name, --auto-prune, --tags)",
 	Args:  cobra.ExactArgs(1),
 	RunE: func(cmd *cobra.Command, args []string) error {
 		c, err := client()
@@ -97,8 +98,18 @@ var nodesUpdateCmd = &cobra.Command{
 		if cmd.Flags().Changed("auto-prune") {
 			body["auto_prune"], _ = cmd.Flags().GetBool("auto-prune")
 		}
+		if cmd.Flags().Changed("tags") {
+			raw, _ := cmd.Flags().GetString("tags")
+			tags := []string{}
+			for _, t := range strings.Split(raw, ",") {
+				if t = strings.TrimSpace(t); t != "" {
+					tags = append(tags, t)
+				}
+			}
+			body["tags"] = tags
+		}
 		if len(body) == 0 {
-			return &APIError{Message: "nothing to update — pass --name or --auto-prune", ExitCode: ExitError}
+			return &APIError{Message: "nothing to update — pass --name, --auto-prune or --tags", ExitCode: ExitError}
 		}
 		data, err := c.Do("PUT", "/agents/"+args[0], body)
 		if err != nil {
@@ -292,6 +303,7 @@ var nodeTokensRevokeCmd = &cobra.Command{
 func init() {
 	nodesUpdateCmd.Flags().String("name", "", "node display name")
 	nodesUpdateCmd.Flags().Bool("auto-prune", false, "enqueue a daily bounded docker prune")
+	nodesUpdateCmd.Flags().String("tags", "", "comma-separated placement tags (services with placement_tags only schedule onto matching nodes)")
 	nodesPruneCmd.Flags().String("until", "", "only prune objects older than this duration (e.g. 168h)")
 	nodesPruneCmd.Flags().Bool("volumes", false, "also prune volumes (destructive — asks twice)")
 	nodeTokensCmd.AddCommand(nodeTokensIssueCmd, nodeTokensListCmd, nodeTokensRevokeCmd)

app/backend/internal/cli/commands/services.go

@@ -117,6 +117,15 @@ var servicesCreateCmd = &cobra.Command{
 		if v, _ := cmd.Flags().GetBool("spread"); v {
 			body["spread"] = v
 		}
+		if v, _ := cmd.Flags().GetString("placement-tags"); v != "" {
+			tags := []string{}
+			for _, t := range strings.Split(v, ",") {
+				if t = strings.TrimSpace(t); t != "" {
+					tags = append(tags, t)
+				}
+			}
+			body["placement_tags"] = tags
+		}
 		data, err := c.Do("POST", "/projects/"+args[0]+"/services", body)
 		if err != nil {
 			return err
@@ -210,6 +219,16 @@ var servicesUpdateCmd = &cobra.Command{
 			v, _ := cmd.Flags().GetBool("spread")
 			body["spread"] = v
 		}
+		if cmd.Flags().Changed("placement-tags") {
+			v, _ := cmd.Flags().GetString("placement-tags")
+			tags := []string{}
+			for _, t := range strings.Split(v, ",") {
+				if t = strings.TrimSpace(t); t != "" {
+					tags = append(tags, t)
+				}
+			}
+			body["placement_tags"] = tags
+		}
 		if cmd.Flags().Changed("sleep-idle") {
 			v, _ := cmd.Flags().GetInt("sleep-idle")
 			body["sleep_idle_minutes"] = v
@@ -503,6 +522,7 @@ func init() {
 	f.String("static-dir", "", "output dir for the static builder (default dist)")
 	f.String("node", "", "pin to a node agent id, or 'auto' for least-loaded (image services only)")
 	f.Bool("spread", false, "distribute replicas across all online schedulable nodes")
+	f.String("placement-tags", "", "comma-separated node tags required for remote placement (auto/spread only)")
 
 	uf := servicesUpdateCmd.Flags()
 	uf.String("name", "", "service name")
@@ -529,6 +549,7 @@ func init() {
 	uf.Int("sleep-idle", 0, "idle minutes before sleeping (1-1440)")
 	uf.String("node", "", "pin to a node agent id, 'auto' for least-loaded, 'local' to clear")
 	uf.Bool("spread", false, "spread replicas across all online schedulable nodes (--spread=false to disable)")
+	uf.String("placement-tags", "", "comma-separated node tags required for remote placement (empty clears)")
 
 	for _, a := range []string{"start", "stop", "restart", "redeploy", "sleep", "wake"} {
 		verb := a