Merge pull request #509 from hildebrandttk/feat/unified-mailbox-account-scope

Feat/unified mailbox account scope

Rework the sidebar "All accounts" into an account-bounded "Unified Mailbox"
by default, with cross-account merging as an opt-in (admin-gated) sub-option.
The standalone per-account "All Mail" virtual folder is folded into the unified
All mail / Unread / Starred entries.

Conflict resolution notes:
- stores/settings-store.ts: both main and this branch independently added a
  per-account default-identity (#507) migration at different versions (main v6,
  branch v7). Merged migration is version 7 using the refactored migrateSettings
  function; the unified-mailbox rework is guarded at `version < 7` so users who
  stopped at main's interim v6 identity bump still receive it, while the #507
  identity-map coercion stays at `version < 6` so their populated map is kept.
- stores/auth-store.ts: kept main's applyPreferredIdentity (superset with the
  pre-#507 legacy migration).
- stores/email-store.ts: removed the ALL_MAIL_MAILBOX_ID paths (folded into the
  unified views) while preserving main's plugin hooks (onSearchResults /
  onEmailsFetched); adopted advancedSearchCrossViewEmails for advanced cross-view
  search.
- components/settings/layout-settings.tsx: kept main's faviconUnreadBadge setting
  alongside the new unifiedCrossAccount toggle.
- integration/: union-merged the two independently-authored suites - branch suite
  is authoritative (matches new behavior) with main's shared-identity (#569) group
  infrastructure preserved.
- components/email/email-composer.tsx: dropped a duplicate data-testid attribute
  introduced by the auto-merge.

integration/README.md

@@ -80,9 +80,46 @@ integration/
     │   └── app.ts                # login, add/switch account, folder-counter reads
     ├── 01-login.spec.ts
     ├── 02-mail-sync.spec.ts      # single-account: receive/read/move/delete/folder-create
-    └── 03-multi-account.spec.ts  # isolation + cross-account Unified Inbox aggregation
+    ├── 03-multi-account.spec.ts  # isolation + cross-account Unified Inbox aggregation
+    ├── 04-all-mail.spec.ts       # All Mail view: single-account merge + cross-account
+    ├── 04-shared-identity.spec.ts# composer From offers shared/group send-as identities (issue #569)
+    ├── 05-actions.spec.ts        # context-menu read/unread, delete, spam (inbox)
+    ├── 06-shared-folders.spec.ts # delegated folder: appears + read/unread/delete/spam
+    ├── 07-drafts.spec.ts         # multiple recipients, changed sender, continue-draft button
+    ├── 08-shared-moves.spec.ts   # moving mail across own/shared and shared/shared
+    ├── 09-live-counters.spec.ts  # live unified/All-Mail counters (login + shared)
+    └── 10-attachments.spec.ts    # cross-account attachment download from All Mail
 ```
 
+## Findings surfaced by the suite
+
+Some tests assert server-side truth (or use `test.fail` to pin a known gap)
+because the UI behaviour is currently incomplete. Worth a look:
+
+- **Shared-account counters now reconcile on focus/interval** (`09-live-counters`).
+  Stalwart's SSE only pushes StateChange for the *primary* account, so a
+  background change in a shared/delegated account is never pushed. The client
+  now also polls the session's secondary accounts, so their folder badges and
+  the unified/All-Mail counter refresh on the visibility reconcile and on a slow
+  background poll. (A *login* account already updates live via its own SSE.)
+  Note: these shared counters still don't update the instant a local action
+  runs — they follow the reconcile, not the optimistic path.
+- **`mark-as-spam` doesn't optimistically decrement the source counter** the
+  way `delete` does; it settles after a reconcile.
+- **Reopening a draft resets the From selector** to the default identity even
+  though the draft was saved with (and the server retains) the chosen sender.
+  Pinned with `test.fail` in `07-drafts`.
+- **Cross-account moves (own ⇆ shared folder) don't relocate the message.** The
+  "Move to" submenu offers the shared folder, but clicking it is a no-op.
+  Shared ⇆ shared (same owner) moves work. Pinned with `test.fail` in
+  `08-shared-moves`.
+- **Cross-account attachments & inline images (fixed).** Blobs are account-
+  scoped, so viewing/downloading/previewing an attachment, rendering an inline
+  `cid:` image, dragging out, and the bundle/S-MIME/TNEF/embedded-message
+  fetches on an All-Mail message from another account 404'd against the active
+  account. Every viewer blob fetch now routes to the message's owning client +
+  accountId (`10-attachments` covers download + inline image).
+
 ## How the tests work
 
 - **Mutations** are made out-of-band — mail is injected over SMTP