fix(worklog): always send logged_date (required datetime) on worklog add

The backend's WorkLogCreate.logged_date is a REQUIRED datetime, but the CLI
only sent it when --date was passed, and then as a bare YYYY-MM-DD that
failed datetime parsing → `hf worklog add` always 422'd (missing, then
invalid). Default logged_date to now (RFC3339); anchor a bare --date
<yyyy-mm-dd> to start-of-day so it parses as a datetime.

Verified on sim: `hf worklog add --task <code> --hours <n> --desc ...`
(no --date) now succeeds.

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

internal/commands/worklog.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"time"
 
 	"git.hangman-lab.top/zhi/HarborForge.Cli/internal/output"
 )
@@ -35,9 +36,18 @@ func RunWorklogAdd(taskCode string, hours float64, desc, date, tokenFlag string)
 	if desc != "" {
 		payload["description"] = desc
 	}
+	// logged_date is a REQUIRED datetime on the backend. Default to now; if
+	// the operator passed --date <yyyy-mm-dd>, anchor it to start-of-day so a
+	// bare date still parses as a datetime.
+	loggedDate := time.Now().UTC().Format(time.RFC3339)
 	if date != "" {
-		payload["logged_date"] = date
+		if len(date) == 10 { // bare YYYY-MM-DD
+			loggedDate = date + "T00:00:00Z"
+		} else {
+			loggedDate = date
 		}
+	}
+	payload["logged_date"] = loggedDate
 
 	body, err := json.Marshal(payload)
 	if err != nil {