merge(develop): retain active-work guards with immutable Ticket evidence

T-716: incorporate T-715 (b6de908e) into the existing Ticket source branch only. Resolve MR read/readiness conflicts by keeping persisted merged-result evaluation and active assignment selection for open source observation. Preserve responsibility records and terminal work releases. Update temporary API regression fixtures to distinguish retained identity from active work.

Narrow validation: merge-request store 21 tests; Workspace Server Ticket evidence API 5 tests, including done/merged remote evidence without active assignment and unavailable open source with retained released responsibility.

crates/worker/src/feature/builtin/manage_worker.rs

@@ -875,7 +875,7 @@ impl WorkerOperation {
                 "Restore a stopped Backend/Runtime Worker session in the current Workspace. Supply expected_observation_token from WorkerList; a conflict requires refreshing and deliberate new intent. New requests default to the durable Tool call ID. For explicit recovery of an unknown/pending outcome, supply the reported request_id and the original token unchanged; never create a new intent or automatically retry."
             }
             Self::Remove => {
-                "Remove an eligible stopped, unassigned, non-internal Worker. Supply a bounded reason; Backend validation and retention are authoritative."
+                "Remove an eligible stopped, non-internal Worker with no unfinished Ticket work. Terminal Ticket responsibility is retained and does not require unassignment. Supply a bounded reason; Backend validation and retention are authoritative."
             }
         }
     }

crates/worker/src/feature/builtin/merge_request.rs

@@ -1149,7 +1149,7 @@ pub fn description(n: &str) -> Option<&'static str> {
             "Record Orchestrator-owned integration for the explicitly addressed Merge Request without completing the Ticket or releasing its assignment.",
         ),
         "CompleteTicket" => Some(
-            "Complete the Ticket only after reviewing its current item revision and exact linked Merge Request result set; this releases the current assignment atomically.",
+            "Complete the Ticket only after reviewing its current item revision and exact linked Merge Request result set; this ends unfinished work atomically while retaining responsibility and assignment history.",
         ),
         "ReviewMergeRequest" => Some(
             "Submit the injected Reviewer capability result for its captured exact source ref; source movement cancels it, while target-only movement does not.",

crates/worker/src/prompt/catalog.rs

@@ -1027,7 +1027,7 @@ mod tests {
     }
 
     #[test]
-    fn builtin_orchestrator_cleanup_policy_renders_with_common_includes() {
+    fn builtin_orchestrator_cleanup_retains_terminal_responsibility_and_blocks_unfinished_work() {
         let rendered = PromptCatalog::builtins_only()
             .unwrap()
             .render_name("role.orchestrator", Value::UNDEFINED)
@@ -1040,7 +1040,21 @@ mod tests {
         assert!(rendered.contains("call `WorkerStop`"));
         assert!(rendered.contains("call `WorkerRemove`"));
         assert!(rendered.contains("only then call `WorkdirDelete`"));
-        assert!(rendered.contains("`CurrentAssignment` means unassign and reread"));
+        assert!(rendered.contains("must have no unfinished Ticket work"));
+        assert!(rendered.contains("does not require unassignment before cleanup"));
+        assert!(rendered.contains("`UnfinishedWork` (`unfinished_work` on the wire)"));
+        assert!(rendered.contains("requires explicit work end or reassignment"));
+        assert!(rendered.contains("idle or stopped status does not end unfinished work"));
+        for stale_policy in [
+            "no current Ticket assignment",
+            "unassign it through the available orchestration authority",
+            "`CurrentAssignment`",
+        ] {
+            assert!(
+                !rendered.contains(stale_policy),
+                "stale cleanup policy: {stale_policy}"
+            );
+        }
         assert!(!rendered.contains("{% include"));
     }
 }