fix(milestone): use nested /projects/{project}/milestones routes + datetime due

Two contract bugs broke `hf milestone *` against the backend:

- The backend mounts milestones at prefix /projects/{project_id}/milestones
  (nested), but the CLI used flat /milestones, /milestones/<code>, etc. →
  every milestone create/get/update/delete/progress/list 404'd. Switch to
  the nested routes: list/create take --project; get/update/delete/progress
  derive the project from the milestone code (PFIXTU:00001 → PFIXTU) via a
  new milestoneProject() helper. list now requires --project.
- due_date is a REQUIRED datetime on the backend, but --due <yyyy-mm-dd>
  was sent date-only → 422 datetime_parsing. Anchor a bare date to
  start-of-day (toMilestoneDateTime), same as the worklog logged_date fix.

Verified on sim: milestone create/list/get/progress all succeed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/commands/milestone.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"strings"
 
 	"git.hangman-lab.top/zhi/HarborForge.Cli/internal/client"
 	"git.hangman-lab.top/zhi/HarborForge.Cli/internal/config"
@@ -32,11 +33,30 @@ type milestoneProgressResponse struct {
 	Progress   float64 `json:"progress"`
 }
 
+// milestoneProject extracts the project code from a milestone code
+// (e.g. "PFIXTU:00001" -> "PFIXTU"); milestones are nested under their
+// project in the API (/projects/{project}/milestones/{code}).
+func milestoneProject(code string) string {
+	if i := strings.IndexByte(code, ':'); i >= 0 {
+		return code[:i]
+	}
+	return code
+}
+
+// toMilestoneDateTime anchors a bare YYYY-MM-DD due date to a datetime, since
+// the backend's due_date field requires a full datetime.
+func toMilestoneDateTime(d string) string {
+	if len(d) == 10 {
+		return d + "T00:00:00Z"
+	}
+	return d
+}
+
 // RunMilestoneList implements `hf milestone list --project <project-code>`.
 func RunMilestoneList(args []string, tokenFlag string) {
 	token := ResolveToken(tokenFlag)
 
-	query := ""
+	query, project := "", ""
 	for i := 0; i < len(args); i++ {
 		switch args[i] {
 		case "--project":
@@ -44,7 +64,7 @@ func RunMilestoneList(args []string, tokenFlag string) {
 				output.Error("--project requires a value")
 			}
 			i++
-			query = appendQuery(query, "project_code", args[i])
+			project = args[i]
 		case "--status":
 			if i+1 >= len(args) {
 				output.Error("--status requires a value")
@@ -66,8 +86,11 @@ func RunMilestoneList(args []string, tokenFlag string) {
 	if err != nil {
 		output.Errorf("config error: %v", err)
 	}
+	if project == "" {
+		output.Error("--project is required (milestones are listed per project)")
+	}
 	c := client.New(cfg.BaseURL, token)
-	path := "/milestones"
+	path := "/projects/" + project + "/milestones"
 	if query != "" {
 		path += "?" + query
 	}
@@ -110,7 +133,7 @@ func RunMilestoneGet(milestoneCode, tokenFlag string) {
 		output.Errorf("config error: %v", err)
 	}
 	c := client.New(cfg.BaseURL, token)
-	data, err := c.Get("/milestones/" + milestoneCode)
+	data, err := c.Get("/projects/" + milestoneProject(milestoneCode) + "/milestones/" + milestoneCode)
 	if err != nil {
 		output.Errorf("failed to get milestone: %v", err)
 	}
@@ -196,7 +219,7 @@ func RunMilestoneCreate(args []string, tokenFlag string) {
 		payload["description"] = desc
 	}
 	if due != "" {
-		payload["due_date"] = due
+		payload["due_date"] = toMilestoneDateTime(due)
 	}
 
 	body, err := json.Marshal(payload)
@@ -209,7 +232,7 @@ func RunMilestoneCreate(args []string, tokenFlag string) {
 		output.Errorf("config error: %v", err)
 	}
 	c := client.New(cfg.BaseURL, token)
-	data, err := c.Post("/milestones", bytes.NewReader(body))
+	data, err := c.Post("/projects/"+project+"/milestones", bytes.NewReader(body))
 	if err != nil {
 		output.Errorf("failed to create milestone: %v", err)
 	}
@@ -261,7 +284,7 @@ func RunMilestoneUpdate(milestoneCode string, args []string, tokenFlag string) {
 				output.Error("--due requires a value")
 			}
 			i++
-			payload["due_date"] = args[i]
+			payload["due_date"] = toMilestoneDateTime(args[i])
 		default:
 			output.Errorf("unknown flag: %s", args[i])
 		}
@@ -281,7 +304,7 @@ func RunMilestoneUpdate(milestoneCode string, args []string, tokenFlag string) {
 		output.Errorf("config error: %v", err)
 	}
 	c := client.New(cfg.BaseURL, token)
-	_, err = c.Patch("/milestones/"+milestoneCode, bytes.NewReader(body))
+	_, err = c.Patch("/projects/"+milestoneProject(milestoneCode)+"/milestones/"+milestoneCode, bytes.NewReader(body))
 	if err != nil {
 		output.Errorf("failed to update milestone: %v", err)
 	}
@@ -297,7 +320,7 @@ func RunMilestoneDelete(milestoneCode, tokenFlag string) {
 		output.Errorf("config error: %v", err)
 	}
 	c := client.New(cfg.BaseURL, token)
-	_, err = c.Delete("/milestones/" + milestoneCode)
+	_, err = c.Delete("/projects/" + milestoneProject(milestoneCode) + "/milestones/" + milestoneCode)
 	if err != nil {
 		output.Errorf("failed to delete milestone: %v", err)
 	}
@@ -312,7 +335,7 @@ func RunMilestoneProgress(milestoneCode, tokenFlag string) {
 		output.Errorf("config error: %v", err)
 	}
 	c := client.New(cfg.BaseURL, token)
-	data, err := c.Get("/milestones/" + milestoneCode + "/progress")
+	data, err := c.Get("/projects/" + milestoneProject(milestoneCode) + "/milestones/" + milestoneCode + "/progress")
 	if err != nil {
 		output.Errorf("failed to get milestone progress: %v", err)
 	}