feat: add Gmail Pub/Sub watcher for inbound email automation

New ChannelAdapter that monitors Gmail via Google Cloud Pub/Sub push
notifications with polling fallback. Supports OAuth2 auth, configurable
watch labels, template rendering with email metadata placeholders
(from, to, subject, snippet, date, id, labels).

Wired into daemon lifecycle and gateway (POST /gmail/push endpoint).
Includes 16 tests covering auth, templates, push notifications, and
channel routing.

src/config/schema.ts

@@ -119,6 +119,20 @@ const webhookSchema = z.object({
   enabled: z.boolean().default(true),
 });
 
+const gmailSchema = z.object({
+  enabled: z.boolean().default(false),
+  credentials_file: z.string().optional(),
+  token_file: z.string().default('~/.config/flynn/gmail-token.json'),
+  watch_labels: z.array(z.string()).default(['INBOX']),
+  poll_interval: z.string().default('60s'),
+  history_start: z.string().optional(),  // ISO date string — only process emails after this date
+  output: z.object({
+    channel: z.string().min(1),
+    peer: z.string().min(1),
+  }),
+  message: z.string().default('New email from {{from}}: {{subject}}\n\n{{snippet}}'),
+}).optional();
+
 const heartbeatCheckSchema = z.enum(['gateway', 'model', 'channels', 'memory', 'disk']);
 
 const heartbeatSchema = z.object({
@@ -136,6 +150,7 @@ const heartbeatSchema = z.object({
 const automationSchema = z.object({
   cron: z.array(cronJobSchema).default([]),
   webhooks: z.array(webhookSchema).default([]),
+  gmail: gmailSchema,
   heartbeat: heartbeatSchema,
 }).default({});
 
@@ -343,6 +358,7 @@ export type TelegramConfig = z.infer<typeof telegramSchema>;
 export type ModelConfig = z.infer<typeof modelConfigSchema>;
 export type CronJobConfig = z.infer<typeof cronJobSchema>;
 export type WebhookConfig = z.infer<typeof webhookSchema>;
+export type GmailConfig = z.infer<typeof gmailSchema>;
 export type AgentsConfig = z.infer<typeof agentsSchema>;
 export type CompactionConfig = z.infer<typeof compactionSchema>;
 export type MemoryConfig = z.infer<typeof memorySchema>;