feat: planning pass counts all folders up front for account-wide progress

Before copying, EXAMINE every folder to sum the account's total message count
and emit a 'plan' event; progress events now carry account_total so the UI
shows a real overall bar, percent and ETA (not just per-folder).

- imapx.FolderMessageCount: read-only count of a folder
- orchestrator: plan pass + grandTotal, plan event, account_total in progress
- web: live progress keyed on account total; PLAN log line; overall bar/ETA

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMHQTtnQtQqL8muAXHr9kd

internal/imapx/account.go

@@ -3,9 +3,21 @@ package imapx
 import (
 	"context"
 
+	"github.com/emersion/go-imap/v2"
 	"github.com/emersion/go-imap/v2/imapclient"
 )
 
+// FolderMessageCount opens a folder read-only (EXAMINE) and returns how many
+// messages it holds — used to plan an accurate overall progress total before
+// copying begins. It does not fetch any message bodies.
+func FolderMessageCount(c *imapclient.Client, folder string) (int64, error) {
+	sel, err := c.Select(folder, &imap.SelectOptions{ReadOnly: true}).Wait()
+	if err != nil {
+		return 0, err
+	}
+	return int64(sel.NumMessages), nil
+}
+
 // ListFolders returns the mailbox names visible on an already-connected, logged-in client.
 func ListFolders(c *imapclient.Client) ([]string, error) {
 	mboxes, err := c.List("", "*", nil).Collect()

internal/orchestrator/orchestrator.go

@@ -267,6 +267,33 @@ func (o *Orchestrator) runAccount(ctx context.Context, task store.Task, runID in
 		return o.accountFailed(ctx, task.ID, a, srcEP, dstEP, "src", err)
 	}
 
+	// Planning pass: EXAMINE every folder up front to learn the total message
+	// count, so the UI can show an accurate overall bar / ETA before copying.
+	type folderPlan struct {
+		src, dst string
+		total    int64
+	}
+	plan := make([]folderPlan, 0, len(folders))
+	var grandTotal int64
+	for _, folder := range folders {
+		if actx.Err() != nil {
+			break
+		}
+		df := folder
+		if m, ok := task.FolderMapping[folder]; ok {
+			df = m
+		}
+		n, cerr := imapx.FolderMessageCount(src, folder)
+		if cerr != nil && actx.Err() == nil {
+			slog.Warn("count folder failed", "account", a.ID, "folder", folder, "err", cerr)
+		}
+		plan = append(plan, folderPlan{src: folder, dst: df, total: n})
+		grandTotal += n
+	}
+	o.hub.Publish(wshub.Event{Type: "plan", TaskID: task.ID, Data: map[string]any{
+		"account_id": a.ID, "src_login": a.SrcLogin, "folders": len(plan), "total": grandTotal,
+	}})
+
 	var copied, skipped, errs int64
 	// Account-level live progress state (all callbacks run on this goroutine,
 	// so plain vars are race-free). base* = totals from completed folders;
@@ -287,12 +314,13 @@ func (o *Orchestrator) runAccount(ctx context.Context, task store.Task, runID in
 			}
 			lastEmit = now
 			o.hub.Publish(wshub.Event{Type: "progress", TaskID: task.ID, Data: map[string]any{
-				"account_id": a.ID,
-				"copied":     baseCopied + int64(c),
-				"skipped":    baseSkipped + int64(s),
-				"folder":     curFolder,
-				"folder_done":  done,
-				"folder_total": curTotal,
+				"account_id":    a.ID,
+				"copied":        baseCopied + int64(c),
+				"skipped":       baseSkipped + int64(s),
+				"folder":        curFolder,
+				"folder_done":   done,
+				"folder_total":  curTotal,
+				"account_total": grandTotal,
 			}})
 		},
 		// Fires after EXAMINE (before the long fetch) with the folder's message count.
@@ -304,20 +332,16 @@ func (o *Orchestrator) runAccount(ctx context.Context, task store.Task, runID in
 			}})
 		},
 	}
-	for _, folder := range folders {
+	for _, fp := range plan {
 		if actx.Err() != nil {
 			break // cancelled — stop scheduling more folders
 		}
-		dstFolder := folder
-		if m, ok := task.FolderMapping[folder]; ok {
-			dstFolder = m
-		}
-		res, err := imapx.CopyFolder(actx, src, dst, folder, dstFolder, deps)
+		res, err := imapx.CopyFolder(actx, src, dst, fp.src, fp.dst, deps)
 		if err != nil && actx.Err() == nil {
-			slog.Warn("folder copy error", "account", a.ID, "src_login", a.SrcLogin, "folder", folder, "err", err)
+			slog.Warn("folder copy error", "account", a.ID, "src_login", a.SrcLogin, "folder", fp.src, "err", err)
 			errs++
 			o.hub.Publish(wshub.Event{Type: "error", TaskID: task.ID, Data: map[string]any{
-				"account_id": a.ID, "src_login": a.SrcLogin, "folder": folder, "error": err.Error(),
+				"account_id": a.ID, "src_login": a.SrcLogin, "folder": fp.src, "error": err.Error(),
 			}})
 		}
 		copied += int64(res.Copied)