feat(sessions): add channelIdleMinutes config for per-channel session idle durations (#1353)

* feat(sessions): add channelIdleMinutes config for per-channel session idle durations

Add new `channelIdleMinutes` config option to allow different session idle
timeouts per channel. For example, Discord sessions can now be configured
to last 7 days (10080 minutes) while other channels use shorter defaults.

Config example:
  sessions:
    channelIdleMinutes:
      discord: 10080  # 7 days

The channel-specific idle is passed as idleMinutesOverride to the existing
resolveSessionResetPolicy, integrating cleanly with the new reset policy
architecture.

* fix

* feat: add per-channel session reset overrides (#1353) (thanks @cash-echo-bot)

---------

Co-authored-by: Cash Williams <cashwilliams@gmail.com>
Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/config/types.base.ts

@@ -77,9 +77,10 @@ export type SessionConfig = {
   identityLinks?: Record<string, string[]>;
   resetTriggers?: string[];
   idleMinutes?: number;
-  heartbeatIdleMinutes?: number;
   reset?: SessionResetConfig;
   resetByType?: SessionResetByTypeConfig;
+  /** Channel-specific reset overrides (e.g. { discord: { mode: "idle", idleMinutes: 10080 } }). */
+  resetByChannel?: Record<string, SessionResetConfig>;
   store?: string;
   typingIntervalSeconds?: number;
   typingMode?: TypingMode;