Deploy multi-file Hub workflows (#3128)

* feat(hub): deploy canonical workflow bundles

Keep CLI deployment aligned with Hub's authored bundle boundary so validation and activation receive the same deterministic source files. Public documentation now teaches that boundary as the only configuration format.

* test(hub): assert validation diagnostics directly

* refactor(hub): deepen HTTP client module

* feat(hub): validate named agent configurations

* docs(hub): align Claude mode example

public-docs/hub/triggers/index.md

@@ -10,30 +10,28 @@ category: Hub
 
 A trigger says which provider event can start a workflow. The [Hub workflows](/docs/hub/workflows) page covers the steps, inputs, routing, prompts, and deadlines that run after a match.
 
+`.paseo/workflows/github-mention.yml`:
+
 ```yaml
-triggers:
-  - name: mention
-    on: github.issue_comment
-    filters:
-      repo: acme/api
-      contains: "@paseo"
-      from_users: [alice]
-    max_runtime: 2h
-    steps:
-      - id: work
-        environment: dev
-        max_runtime: 90m
-        idle_timeout: 10m
-        agent: { provider: codex, mode: full-access }
-        prompt:
-          - text: Call hub.finish_execution when the step is complete.
-          - text: |
-              <user-prompt>
-              ${{ paseo.prompt }}
-              </user-prompt>
+name: mention
+on: github.issue_comment
+filters:
+  repo: acme/api
+  contains: "@paseo"
+  from_users: [alice]
+max_runtime: 2h
+steps:
+  - id: work
+    environment: dev
+    max_runtime: 90m
+    idle_timeout: 10m
+    agent: codex
+    prompt:
+      - text: Call hub.finish_execution when the step is complete.
+      - text: ${{ paseo.prompt }}
 ```
 
-Field-by-field detail is in the [`hub.yml` reference](/docs/hub/configuration/hub-yml).
+Field-by-field detail is in the [configuration reference](/docs/hub/configuration/hub-yml).
 
 ## Events