fix(dashboard): replace stale 'manager' with 'submitter' in approval UI text

Two operator-visible strings and one code comment still referenced 'the
manager' in the approval card UI:

- init_config card description: 'manager customises agent.nix before
  spawn' -> 'submitting agent customises agent.nix before spawn'
- deny form data-prompt: 'sent to manager' -> 'sent to submitter'
  (the deny note goes to the ApprovalResolved submitter, not a fixed
  manager role)
- code comment: 'surfaced to the manager via' -> 'surfaced to the
  submitting agent via'
- builds.html meta text: 'manager learns each outcome' -> 'the
  submitting agent learns each outcome'

The 'manager' role is no longer structural — root-ness is topological.
Any agent with the approvals tool group can submit; the note/event routes
to the submitter.

frontend/packages/dashboard/src/builds.html

@@ -58,7 +58,7 @@
     <!-- M3T4 1NPUTS: select inputs to nix flake update in /meta/. -->
     <section class="builds-pane" id="builds-pane-meta" data-tab-pane="meta"
              role="tabpanel" aria-labelledby="builds-tab-meta">
-      <p class="meta">select inputs to <code>nix flake update</code> in <code>/meta/</code>. selected agents rebuild in sequence after the lock bump; manager learns each outcome via the usual <code>rebuilt</code> system event.</p>
+      <p class="meta">select inputs to <code>nix flake update</code> in <code>/meta/</code>. selected agents rebuild in sequence after the lock bump; the submitting agent learns each outcome via the usual <code>rebuilt</code> system event.</p>
       <div id="meta-inputs-section">
         <p class="meta">loading…</p>
       </div>