feat(gmail): add signature support to send command

README.md

@@ -531,6 +531,9 @@ gog gmail send --to a@b.com --subject "Hi" --body "Plain fallback"
 gog gmail send --to a@b.com --subject "Hi" --body-file ./message.txt
 gog gmail send --to a@b.com --subject "Hi" --body-file -   # Read body from stdin
 gog gmail send --to a@b.com --subject "Hi" --body "Plain fallback" --body-html "<p>Hello</p>"
+gog gmail send --to a@b.com --subject "Hi" --body "Plain fallback" --signature
+gog gmail send --to a@b.com --subject "Hi" --body-html "<p>Hello</p>" --signature-name alias@example.com
+gog gmail send --to a@b.com --subject "Hi" --body "Plain fallback" --signature-file ./signature.txt
 gog gmail drafts list
 gog gmail drafts create --subject "Draft" --body "Body"
 gog gmail drafts create --to a@b.com --subject "Draft" --body "Body"

docs/spec.md

@@ -260,7 +260,7 @@ Flag aliases:
 - `gog gmail labels get <labelIdOrName>`
 - `gog gmail labels create <name>`
 - `gog gmail labels modify <threadIds...> [--add ...] [--remove ...]`
-- `gog gmail send --to a@b.com --subject S [--body B] [--body-html H] [--cc ...] [--bcc ...] [--reply-to-message-id <messageId>] [--reply-to addr] [--attach <file>...]`
+- `gog gmail send --to a@b.com --subject S [--body B] [--body-html H] [--cc ...] [--bcc ...] [--reply-to-message-id <messageId>] [--reply-to addr] [--attach <file>...] [--signature|--signature-name EMAIL|--signature-file PATH]`
 - `gog gmail drafts list [--max N] [--page TOKEN]`
 - `gog gmail drafts get <draftId> [--download]`
 - `gog gmail drafts create --subject S [--to a@b.com] [--body B] [--body-html H] [--cc ...] [--bcc ...] [--reply-to-message-id <messageId>] [--reply-to addr] [--attach <file>...]`

docs/watch.md

@@ -48,7 +48,8 @@ gog gmail watch serve \
   [--verify-oidc] [--oidc-email <svc@...>] [--oidc-audience <aud>] \
   [--token <shared>] \
   [--hook-url <url>] [--hook-token <token>] \
-  [--include-body] [--max-bytes <n>] [--save-hook]
+  [--include-body] [--max-bytes <n>] \
+  [--history-types <type>...] [--save-hook]
 
 gog gmail history --since <historyId> [--max <n>] [--page <token>]
 ```
@@ -58,6 +59,7 @@ Notes:
 - `watch renew` reuses stored topic/labels.
 - `watch stop` calls Gmail stop + clears state.
 - `watch serve` uses stored hook if `--hook-url` not provided.
+- `watch serve --history-types` accepts `messageAdded`, `messageDeleted`, `labelAdded`, `labelRemoved` (repeatable or comma-separated). Default: `messageAdded` (for backward compatibility).
 
 ## State
 

internal/cmd/admin_directory_helpers.go

@@ -0,0 +1,14 @@
+package cmd
+
+import "os"
+
+// adminCustomerID returns the customer ID for Admin SDK calls.
+// Defaults to "my_customer" (the authenticated admin's domain) but
+// can be overridden via the GOG_CUSTOMER_ID environment variable
+// for multi-tenant administration.
+func adminCustomerID() string {
+	if id := os.Getenv("GOG_CUSTOMER_ID"); id != "" {
+		return id
+	}
+	return "my_customer"
+}