Revert reviewer/approver pickers to sidebar, add to new-issue chip bar

Per feedback: reviewer/approver pickers were incorrectly placed in the
issue header row. This moves them back to the Properties sidebar at
regular size and adds them as small chip-style selectors in the
new-issue dialog's bottom bar (next to Upload), matching the existing
chip styling.

- Restored Reviewers/Approvers PropertyPicker rows in IssueProperties
- Removed ExecutionParticipantPicker pills from IssueDetail header
- Added Eye/ShieldCheck-icon reviewer/approver InlineEntitySelectors
  in NewIssueDialog chip bar after Upload button

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/pages/IssueDetail.tsx

@@ -43,7 +43,6 @@ import { InlineEditor } from "../components/InlineEditor";
 import { CommentThread } from "../components/CommentThread";
 import { IssueDocumentsSection } from "../components/IssueDocumentsSection";
 import { IssueProperties } from "../components/IssueProperties";
-import { ExecutionParticipantPicker } from "../components/ExecutionParticipantPicker";
 import { IssueWorkspaceCard } from "../components/IssueWorkspaceCard";
 import { LiveRunWidget } from "../components/LiveRunWidget";
 import type { MentionOption } from "../components/MarkdownEditor";
@@ -1356,23 +1355,6 @@ export function IssueDetail() {
             </div>
           )}
 
-          <div className="flex items-center gap-1">
-            <ExecutionParticipantPicker
-              issue={issue}
-              stageType="review"
-              agents={agents ?? []}
-              currentUserId={currentUserId}
-              onUpdate={(data) => updateIssue.mutate(data)}
-            />
-            <ExecutionParticipantPicker
-              issue={issue}
-              stageType="approval"
-              agents={agents ?? []}
-              currentUserId={currentUserId}
-              onUpdate={(data) => updateIssue.mutate(data)}
-            />
-          </div>
-
           <div className="ml-auto flex items-center gap-0.5 md:hidden shrink-0">
             <Button
               variant="ghost"