refactor(web_chat): name the surface subscribers after their new module (#5002)

The four EventHandler::name() returns still read `channels::web::*`, naming a
module that no longer exists after the relocation. AGENTS.md's convention is
`<domain>::<purpose>`, and sibling subscribers follow it (`cron::delivery`,
`memory::conversations::persistence`).

Log-output only: `name()` is consumed at src/core/event_bus/bus.rs:145,169 and
both uses are tracing fields. Dispatch filters on `domains()`, not `name()`.
Verified nothing keys on the old strings — no classifier, filter, or frontend
reference.

Author: oxoxDev

src/openhuman/web_chat/event_bus.rs

@@ -121,7 +121,7 @@ struct EgressSurfaceSubscriber;
 #[async_trait]
 impl EventHandler for EgressSurfaceSubscriber {
     fn name(&self) -> &str {
-        "channels::web::egress_surface"
+        "web_chat::egress_surface"
     }
 
     fn domains(&self) -> Option<&[&str]> {
@@ -178,7 +178,7 @@ struct ArtifactSurfaceSubscriber;
 #[async_trait]
 impl EventHandler for ArtifactSurfaceSubscriber {
     fn name(&self) -> &str {
-        "channels::web::artifact_surface"
+        "web_chat::artifact_surface"
     }
 
     fn domains(&self) -> Option<&[&str]> {
@@ -326,7 +326,7 @@ struct ApprovalSurfaceSubscriber;
 #[async_trait]
 impl EventHandler for ApprovalSurfaceSubscriber {
     fn name(&self) -> &str {
-        "channels::web::approval_surface"
+        "web_chat::approval_surface"
     }
 
     fn domains(&self) -> Option<&[&str]> {
@@ -411,7 +411,7 @@ struct AutomationHaltSubscriber;
 #[async_trait]
 impl EventHandler for AutomationHaltSubscriber {
     fn name(&self) -> &str {
-        "channels::web::automation_halt"
+        "web_chat::automation_halt"
     }
 
     fn domains(&self) -> Option<&[&str]> {