Server-owned agent completion: remove report_completion dependency

When an agent process exits normally, the server now automatically runs
acceptance gates (uncommitted changes check + cargo clippy + tests) and
advances the pipeline based on results. This replaces the previous model
where agents had to explicitly call report_completion as an MCP tool.

Changes:
- Add run_server_owned_completion() free function in agents.rs that runs
  gates on process exit, stores a CompletionReport, and advances pipeline
- Wire it into start_agent's spawned task (replaces simple status setting)
- Remove report_completion from MCP tools list and handler (mcp.rs)
- Update default_agent_prompt() to not reference report_completion
- Update all agent prompts in project.toml (supervisor, coders, qa,
  mergemaster) to reflect server-owned completion
- Add guard: skip gates if completion was already recorded (legacy path)
- Add 4 new tests for server-owned completion behavior
- Update tools_list test (26 tools, report_completion excluded)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/http/mcp.rs

@@ -582,28 +582,6 @@ fn handle_tools_list(id: Option<Value>) -> JsonRpcResponse {
                         "required": ["worktree_path"]
                     }
                 },
-                {
-                    "name": "report_completion",
-                    "description": "Report that the agent has finished work on a story. Rejects if the worktree has uncommitted changes. Runs acceptance gates (cargo clippy + tests) automatically. Stores the completion status and gate results on the agent record for retrieval by wait_for_agent or the supervisor. Call this as your final action after committing all changes.",
-                    "inputSchema": {
-                        "type": "object",
-                        "properties": {
-                            "story_id": {
-                                "type": "string",
-                                "description": "Story identifier (e.g. '44_my_story')"
-                            },
-                            "agent_name": {
-                                "type": "string",
-                                "description": "Agent name (as configured in project.toml)"
-                            },
-                            "summary": {
-                                "type": "string",
-                                "description": "Brief summary of the work completed"
-                            }
-                        },
-                        "required": ["story_id", "agent_name", "summary"]
-                    }
-                },
                 {
                     "name": "accept_story",
                     "description": "Accept a story: moves it from current/ to archived/ and auto-commits to master.",
@@ -805,8 +783,6 @@ async fn handle_tools_call(
         "remove_worktree" => tool_remove_worktree(&args, ctx).await,
         // Editor tools
         "get_editor_command" => tool_get_editor_command(&args, ctx),
-        // Completion reporting
-        "report_completion" => tool_report_completion(&args, ctx).await,
         // Lifecycle tools
         "accept_story" => tool_accept_story(&args, ctx),
         // Story mutation tools (auto-commit to master)
@@ -1185,40 +1161,6 @@ fn tool_get_editor_command(args: &Value, ctx: &AppContext) -> Result<String, Str
     Ok(format!("{editor} {worktree_path}"))
 }
 
-async fn tool_report_completion(args: &Value, ctx: &AppContext) -> Result<String, String> {
-    let story_id = args
-        .get("story_id")
-        .and_then(|v| v.as_str())
-        .ok_or("Missing required argument: story_id")?;
-    let agent_name = args
-        .get("agent_name")
-        .and_then(|v| v.as_str())
-        .ok_or("Missing required argument: agent_name")?;
-    let summary = args
-        .get("summary")
-        .and_then(|v| v.as_str())
-        .ok_or("Missing required argument: summary")?;
-
-    let report = ctx
-        .agents
-        .report_completion(story_id, agent_name, summary)
-        .await?;
-
-    serde_json::to_string_pretty(&json!({
-        "story_id": story_id,
-        "agent_name": agent_name,
-        "summary": report.summary,
-        "gates_passed": report.gates_passed,
-        "gate_output": report.gate_output,
-        "message": if report.gates_passed {
-            "Completion accepted. All acceptance gates passed."
-        } else {
-            "Completion recorded but acceptance gates failed. Review gate_output for details."
-        }
-    }))
-    .map_err(|e| format!("Serialization error: {e}"))
-}
-
 fn tool_accept_story(args: &Value, ctx: &AppContext) -> Result<String, String> {
     let story_id = args
         .get("story_id")
@@ -1591,7 +1533,7 @@ mod tests {
         assert!(names.contains(&"list_worktrees"));
         assert!(names.contains(&"remove_worktree"));
         assert!(names.contains(&"get_editor_command"));
-        assert!(names.contains(&"report_completion"));
+        assert!(!names.contains(&"report_completion"));
         assert!(names.contains(&"accept_story"));
         assert!(names.contains(&"check_criterion"));
         assert!(names.contains(&"set_test_plan"));
@@ -1601,7 +1543,7 @@ mod tests {
         assert!(names.contains(&"merge_agent_work"));
         assert!(names.contains(&"move_story_to_merge"));
         assert!(names.contains(&"request_qa"));
-        assert_eq!(tools.len(), 27);
+        assert_eq!(tools.len(), 26);
     }
 
     #[test]
@@ -1850,71 +1792,6 @@ mod tests {
         assert!(parsed.get("completion").is_some());
     }
 
-    // ── report_completion tool tests ──────────────────────────────
-
-    #[test]
-    fn report_completion_in_tools_list() {
-        let resp = handle_tools_list(Some(json!(1)));
-        let tools = resp.result.unwrap()["tools"].as_array().unwrap().clone();
-        let tool = tools
-            .iter()
-            .find(|t| t["name"] == "report_completion")
-            .expect("report_completion missing from tools list");
-        // Schema has required fields
-        let required = tool["inputSchema"]["required"].as_array().unwrap();
-        let req_names: Vec<&str> = required.iter().map(|v| v.as_str().unwrap()).collect();
-        assert!(req_names.contains(&"story_id"));
-        assert!(req_names.contains(&"agent_name"));
-        assert!(req_names.contains(&"summary"));
-    }
-
-    #[tokio::test]
-    async fn report_completion_tool_missing_story_id() {
-        let tmp = tempfile::tempdir().unwrap();
-        let ctx = test_ctx(tmp.path());
-        let result =
-            tool_report_completion(&json!({"agent_name": "bot", "summary": "done"}), &ctx).await;
-        assert!(result.is_err());
-        assert!(result.unwrap_err().contains("story_id"));
-    }
-
-    #[tokio::test]
-    async fn report_completion_tool_missing_agent_name() {
-        let tmp = tempfile::tempdir().unwrap();
-        let ctx = test_ctx(tmp.path());
-        let result =
-            tool_report_completion(&json!({"story_id": "44_test", "summary": "done"}), &ctx).await;
-        assert!(result.is_err());
-        assert!(result.unwrap_err().contains("agent_name"));
-    }
-
-    #[tokio::test]
-    async fn report_completion_tool_missing_summary() {
-        let tmp = tempfile::tempdir().unwrap();
-        let ctx = test_ctx(tmp.path());
-        let result = tool_report_completion(
-            &json!({"story_id": "44_test", "agent_name": "bot"}),
-            &ctx,
-        )
-        .await;
-        assert!(result.is_err());
-        assert!(result.unwrap_err().contains("summary"));
-    }
-
-    #[tokio::test]
-    async fn report_completion_tool_nonexistent_agent() {
-        let tmp = tempfile::tempdir().unwrap();
-        let ctx = test_ctx(tmp.path());
-        let result = tool_report_completion(
-            &json!({"story_id": "99_nope", "agent_name": "bot", "summary": "done"}),
-            &ctx,
-        )
-        .await;
-        assert!(result.is_err());
-        let msg = result.unwrap_err();
-        assert!(msg.contains("No agent"), "unexpected: {msg}");
-    }
-
     // ── Editor command tool tests ─────────────────────────────────
 
     #[test]