feat(gmail): take the star off a mail once it has become a task

A starred Gmail message became a task and kept its star, so a starred inbox only
grew — the IMAP side has always unflagged what it imports, and Gmail could not,
because the scope was gmail.readonly. This gives Gmail the same one write: after
the task is made, the STARRED label comes off the message, in one batchModify for
the whole sweep. Nothing else is touched — not the body, not other labels, and a
label trigger's label stays where it is, since that label is the person's own.

The scope goes from gmail.readonly to gmail.modify, which is the narrowest scope
Google offers that can remove a label. An existing connection keeps working on its
old read-only grant — the sync still reads, the unstar is a best-effort 403 that is
logged, not fatal — and starts clearing stars once the account is reconnected and
the new grant is in place. It self-heals: a mail that could not be unstarred stays
starred, stays in the next query, and is tried again.

The consent screen now asks for more than it used to; the settings copy, the docs
and the scope table all say modify rather than read-only in the same change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/httpapi/gmail_test.go

@@ -1,14 +1,17 @@
 package httpapi
 
 import (
-	"github.com/kristianwind/verdande/internal/store"
+	"encoding/json"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"strings"
 	"testing"
 	"time"
 
 	"github.com/kristianwind/verdande/internal/config"
+	"github.com/kristianwind/verdande/internal/store"
 )
 
 // A Gmail failure has to survive being reported.
@@ -150,6 +153,84 @@ func TestASlowMailboxDoesNotHangTheRequest(t *testing.T) {
 	t.Logf("came back in %s with %d", took.Round(time.Millisecond), resp.StatusCode)
 }
 
+// A message that becomes a task has its star taken off — the write that the whole
+// gmail.modify scope is for. The mail's own inbox empties as the tasks are made,
+// the way the IMAP side unflags what it imports.
+func TestASyncedGmailMessageIsUnstarred(t *testing.T) {
+	var unstarred struct {
+		hit  bool
+		body struct {
+			IDs            []string `json:"ids"`
+			RemoveLabelIDs []string `json:"removeLabelIds"`
+		}
+	}
+	google := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.Method == "POST" && strings.HasSuffix(r.URL.Path, "/messages/batchModify"):
+			unstarred.hit = true
+			raw, _ := io.ReadAll(r.Body)
+			_ = json.Unmarshal(raw, &unstarred.body)
+			w.WriteHeader(http.StatusNoContent)
+		case strings.Contains(r.URL.Path, "/messages/") && r.URL.Query().Get("format") == "metadata":
+			writeTestJSON(w, map[string]any{
+				"id": "m1", "threadId": "t1", "snippet": "kort tekst",
+				"payload": map[string]any{"headers": []map[string]string{
+					{"name": "From", "value": "Anders <anders@example.dk>"},
+					{"name": "Subject", "value": "Møde på fredag"},
+				}},
+			})
+		case strings.HasSuffix(r.URL.Path, "/messages"):
+			writeTestJSON(w, map[string]any{"messages": []map[string]string{{"id": "m1"}}})
+		default:
+			http.Error(w, "unexpected "+r.Method+" "+r.URL.Path, http.StatusNotFound)
+		}
+	}))
+	defer google.Close()
+
+	ts := newTestServerWith(t, func(cfg *config.Config) {
+		cfg.GmailClientID = "test-client"
+		cfg.GmailClientSecret = "test-secret"
+		cfg.GoogleTokenURL = google.URL + "/token"
+		cfg.GmailAPIURL = google.URL
+	})
+	ts.bootstrap(t)
+
+	user, err := ts.db.UserByEmail(t.Context(), "kristian@example.dk")
+	if err != nil {
+		t.Fatal(err)
+	}
+	// A live access token, so the run goes straight to the list without a refresh.
+	if err := ts.db.SaveMailbox(t.Context(), &store.Mailbox{
+		UserID: user.ID, Kind: "gmail", RefreshToken: "r", AccessToken: "a",
+		Trigger: "starred", ExpiresAt: time.Now().Add(time.Hour),
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	resp, body := ts.do(t, "POST", "/api/v1/gmail/sync", nil)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("sync: status %d, want 200", resp.StatusCode)
+	}
+	if created, _ := body["created"].(float64); created != 1 {
+		t.Fatalf("created = %v, want 1", body["created"])
+	}
+
+	if !unstarred.hit {
+		t.Fatal("the message was never unstarred; its star is the one thing modify is for")
+	}
+	if strings.Join(unstarred.body.IDs, ",") != "m1" {
+		t.Errorf("unstarred ids = %v, want [m1]", unstarred.body.IDs)
+	}
+	if strings.Join(unstarred.body.RemoveLabelIDs, ",") != "STARRED" {
+		t.Errorf("removed = %v, want [STARRED]", unstarred.body.RemoveLabelIDs)
+	}
+}
+
+func writeTestJSON(w http.ResponseWriter, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	_ = json.NewEncoder(w).Encode(v)
+}
+
 func mustParse(t *testing.T, raw string) *url.URL {
 	t.Helper()
 	u, err := url.Parse(raw)