docs: design notes for /forward and folder-lifecycle features

.scratch/forward-command/design.md

@@ -0,0 +1,54 @@
+# `/forward` — forward a ticket's email thread to a third party
+
+## Goal
+Let staff forward a ticket's entire email conversation to any email address from
+inside the ticket channel. The original customer must **never** be looped in.
+
+## Command
+```
+/forward  email:<address>  [note:<text>]
+```
+- `email` — required destination address; validated with `EMAIL_RE`, header-sanitized.
+- `note` — optional cover message prepended above the transcript (max 1000 chars).
+- Staff-only (the command dispatcher gates every command via `requireStaffRole`);
+  `ManageMessages` default member permission, matching other ticket-mod commands.
+
+## Customer-isolation guarantees (the hard requirement)
+1. `To:` = target address **only**. No `Cc`, no `Bcc`.
+2. The Gmail `messages.send` call carries **no `threadId`** → a brand-new thread,
+   not an append to the customer's conversation.
+3. **No `In-Reply-To` / `References`** headers.
+4. The customer's `senderEmail` is never written into any recipient header.
+5. Fresh `Subject: Fwd: <original subject>`.
+
+## Flow
+- `handlers/commands/forward.js` → `handleForward(interaction)`:
+  1. `findTicketForChannel` — else ephemeral "not a ticket channel".
+  2. Discord-origin ticket (`gmailThreadId` starts `discord-`) → ephemeral "no email thread".
+  3. `deferReply` ephemerally (fetch + attachment download can exceed 3s).
+  4. `forwardThread(gmailThreadId, email, note, userId)`.
+  5. Ephemeral confirmation: "Forwarded N messages (M attachments) to x@y.com"
+     (+ note if any attachments were skipped for size). `logTicketEvent`.
+- `services/gmail.js` → new `forwardThread(threadId, targetEmail, note, userId)`:
+  1. Validate target (`EMAIL_RE`); throw `EBADRECIPIENT` if bad.
+  2. `threads.get(format:'full')`; throw `EEMPTY` if no messages.
+  3. Subject from first message → `Fwd: <subject>` (strip existing `Fwd:`), RFC2047-encode.
+  4. Per message oldest→newest: header line (`From:`/`Date:`) + `getCleanBody`; build
+     parallel text and HTML blocks (HTML body `escapeHtml`-ed — customer content).
+  5. Collect attachment parts (recursive walk for `filename` + `body.attachmentId`);
+     download via `messages.attachments.get`. **Cap total ~20 MB**; past it → skip + count.
+  6. Compose a **new** outbound email: `From: support@`, `To: target only`,
+     `multipart/mixed` (attachments) wrapping `multipart/alternative` (text+html).
+     Plain-ASCII divider between messages in text; `<hr>` in HTML.
+  7. `messages.send` (no `threadId`). Return `{ messageCount, attachmentCount, skipped }`.
+
+## Files
+- `commands/register.js` — `/forward` builder (after `folder`).
+- `services/gmail.js` — `forwardThread()` + `collectAttachmentParts()` helper; export;
+  import `getCleanBody` from `utils`.
+- `handlers/commands/forward.js` — new handler.
+- `handlers/commands/index.js` — import + `COMMAND_HANDLERS.forward`; `/help` line.
+
+## Out of scope
+- Forwarding a single message or letting staff pick one (whole-thread only).
+- Native RFC822 re-send (we build a fresh email instead).