fix(ticket): separate retained responsibility from unfinished work

T-715: end assignment work identities atomically on done/close without deleting responsibility. Reopen never reactivates old authority. Schema 82 preserves legacy closed assignments, historical removal plans and Worker attribution; active work drives admission, auth/routing, retention and cleanup while independent lifecycle/attachment fences remain.

Validation: root cargo check; cargo test -p yoi-workspace-server (630 lib + 11 bin), -p merge-request (20), -p worker (947); worker-runtime restore/removal filters (2); Deno ticket responsibility/runtime UI contracts (12); cargo fmt --all -- --check; git diff --check HEAD.

web/workspace/src/routes/w/[workspaceId]/tickets/[ticketId]/+page.svelte

@@ -519,7 +519,8 @@
 
     <aside class="ticket-control-rail">
       <section class="ticket-control-card ticket-worker-card">
-        <header><h2>Role assignments</h2><span>Server-authoritative</span></header>
+        <header><h2>Role assignments</h2><span>Retained responsibility</span></header>
+        <p class="workspace-empty-copy">Responsibility is retained after work ends and Worker removal; it does not indicate a running Worker or active work authority.</p>
         {#if ticket.assignments.length > 0}
           <ul class="ticket-assignment-list">
             {#each ticket.assignments as assignment}
@@ -538,7 +539,7 @@
             {/each}
           </ul>
         {:else}
-          <p class="workspace-empty-copy">No active role assignment.</p>
+          <p class="workspace-empty-copy">No role responsibility recorded.</p>
         {/if}
         {#if ticket.action_eligibility.can_assign_orchestrator}
           <button

web/workspace/test/ticket-detail-route-reuse.test.ts

@@ -48,3 +48,15 @@ Deno.test("ticket detail fences stale mutation responses", () => {
     assertStringIncludes(operationSource, "generation === routeGeneration");
   }
 });
+
+Deno.test("ticket responsibility display does not claim Worker liveness or work authority", () => {
+  assertStringIncludes(pageSource, "Retained responsibility");
+  assertStringIncludes(pageSource, "after work ends and Worker removal");
+  assertStringIncludes(
+    pageSource,
+    "does not indicate a running Worker or active work authority",
+  );
+  assertStringIncludes(pageSource, "assignment.principal.runtime_id");
+  assertStringIncludes(pageSource, "assignment.principal.worker_id");
+  assert(!pageSource.includes("No active role assignment."));
+});