fix(email): restore the sender identity when reopening a draft

Reopening a draft reset the composer's From to the default identity. The
edit-draft handler matched the draft's saved From against the active-account
identity list by email only, so two identities sharing an address (a default +
an alias differing by name) collided — the wrong one was picked, or with
cross-account namespaced ids none was.

Add findDraftIdentityId (name+email, normalized, +tag fallback) and match against
the same list the composer renders (the flat cross-account list when multi-
account is on). Wired into both the classic and Pro edit-draft paths. Unit tests
plus the un-pinned 07-drafts integration spec.

integration/tests/07-drafts.spec.ts

@@ -120,12 +120,10 @@ test.describe('Drafts', () => {
     expect((draft.from ?? [])[0]?.name, 'draft From carries the selected identity').toBe('Alice Team');
   });
 
-  // KNOWN BUG (documented via test.fail): a draft composed with a non-default
-  // identity is saved with the right From on the server (see the test above),
-  // but reopening the draft resets the composer's From selector to the default
-  // identity instead of restoring the one the draft was written with. If this
-  // starts passing, the reopen path was fixed — flip this back to a plain test.
-  test.fail('reopening a draft restores the changed sender in the From selector', async ({ page }) => {
+  // Regression: reopening a draft must restore the identity it was written with
+  // (drafts store the From address+name, not an identity id, so the reopen path
+  // matches name+address against the identity list — see findDraftIdentityId).
+  test('reopening a draft restores the changed sender in the From selector', async ({ page }) => {
     const altId = await jmap.ensureIdentity('Alice Team', alice.email);
     const subject = subj('draft-from-reopen');