Refactor owner scope across channels and fix default routing fallback (#1151)

* refactor: add explicit owner scope across channels

* fix: tighten routine owner target routing

* fix: address owner scope review feedback

* Fix owner-scope onboarding and event trigger isolation

* Tighten routing fallback and wizard owner validation

* fix: address owner-scope follow-up review

* fix: tighten owner-scope follow-up details

* fix: import Channel trait in telegram test

* fix: normalize http webhook sender ids

* fix: address remaining owner-scope review issues

* fix: reconcile config rebase fallout

* fix: reconcile extension manager rebase drift

* fix: address current copilot review regressions

* fix: restore clippy matrix after rebase

src/agent/routine.rs

@@ -422,8 +422,8 @@ impl Default for RoutineGuardrails {
 pub struct NotifyConfig {
     /// Channel to notify on (None = default/broadcast all).
     pub channel: Option<String>,
-    /// User to notify.
-    pub user: String,
+    /// Explicit target to notify. None means "resolve the owner's last-seen target".
+    pub user: Option<String>,
     /// Notify when routine produces actionable output.
     pub on_attention: bool,
     /// Notify when routine errors.
@@ -436,7 +436,7 @@ impl Default for NotifyConfig {
     fn default() -> Self {
         Self {
             channel: None,
-            user: "default".to_string(),
+            user: None,
             on_attention: true,
             on_failure: true,
             on_success: false,