feat(protocol): wire session aggregation and API with liveness

Finalizing the backend engine for the Operative Protocol.
- Updated agent-sessions.ts to use the deriveLiveness logic and the 15m protocol threshold.
- Integrated the agentLivenessMap into the session aggregation to provide real-time status in the Hub.
- Updated the GET /api/sessions endpoint to fetch and serve liveness metadata.
- Fixed linting warnings (unused imports) in reservations, sessions, and test files.

This commit completes the backend contract for bb-u6f.6.2, providing the data layer necessary for the upcoming 'War Room' UI enhancements.

OPERATIVE: silver-castle
SESSION: 2026-02-14-1145

src/app/api/sessions/route.ts

@@ -1,7 +1,7 @@
 import { NextResponse } from 'next/server';
 import { readIssuesFromDisk } from '../../../lib/read-issues';
 import { activityEventBus } from '../../../lib/realtime';
-import { buildSessionTaskFeed, getCommunicationSummary } from '../../../lib/agent-sessions';
+import { buildSessionTaskFeed, getCommunicationSummary, getAgentLivenessMap } from '../../../lib/agent-sessions';
 
 export const dynamic = 'force-dynamic';
 
@@ -13,8 +13,9 @@ export async function GET(request: Request): Promise<Response> {
     const issues = await readIssuesFromDisk({ projectRoot, preferBd: true });
     const activity = activityEventBus.getHistory(projectRoot);
     const communication = await getCommunicationSummary();
+    const livenessMap = await getAgentLivenessMap();
 
-    const feed = buildSessionTaskFeed(issues, activity, communication);
+    const feed = buildSessionTaskFeed(issues, activity, communication, livenessMap);
 
     return NextResponse.json({ ok: true, feed });
   } catch (error) {

src/lib/agent-reservations.ts

@@ -3,7 +3,6 @@ import os from 'node:os';
 import path from 'node:path';
 
 import { showAgent, deriveLiveness } from './agent-registry';
-import type { AgentRecord } from './agent-registry';
 import type { AgentMessage } from './agent-mail';
 
 const MIN_TTL_MINUTES = 5;

src/lib/agent-sessions.ts

@@ -1,9 +1,9 @@
 import type { ActivityEvent } from './activity';
 import type { BeadIssue } from './types';
-import { listAgents } from './agent-registry';
+import { listAgents, deriveLiveness } from './agent-registry';
 import { inboxAgentMessages, type AgentMessage } from './agent-mail';
 
-export type AgentSessionState = 'active' | 'reviewing' | 'deciding' | 'needs_input' | 'completed' | 'stale';
+export type AgentSessionState = 'active' | 'reviewing' | 'deciding' | 'needs_input' | 'completed' | 'stale' | 'evicted';
 
 export interface SessionTaskCard {
   id: string;
@@ -34,8 +34,21 @@ export interface CommunicationSummary {
   messages: AgentMessage[];
 }
 
-// 24 hours in ms
-const STALE_THRESHOLD_MS = 24 * 60 * 60 * 1000;
+// 15 minutes default stale threshold
+const STALE_THRESHOLD_MS = 15 * 60 * 1000;
+
+export async function getAgentLivenessMap(): Promise<Record<string, string>> {
+  const agentsResult = await listAgents({});
+  const agents = agentsResult.data ?? [];
+  const map: Record<string, string> = {};
+  const now = new Date();
+
+  for (const agent of agents) {
+    map[agent.agent_id] = deriveLiveness(agent.last_seen_at, now);
+  }
+
+  return map;
+}
 
 /**
  * Gathers all relevant communication for all agents to build a summary for aggregation.
@@ -96,7 +109,8 @@ export async function getAgentMetrics(
 export function buildSessionTaskFeed(
   issues: BeadIssue[],
   activity: ActivityEvent[],
-  communicationSummary: CommunicationSummary
+  communicationSummary: CommunicationSummary,
+  agentLivenessMap: Record<string, string> = {}
 ): EpicBucket[] {
   const epics = issues.filter(i => i.issue_type === 'epic');
   const tasks = issues.filter(i => i.issue_type !== 'epic');
@@ -136,11 +150,20 @@ export function buildSessionTaskFeed(
       .sort((a, b) => new Date(b.timestamp).getTime() - new Date(a.timestamp).getTime())[0] ?? null;
   };
 
-  const deriveState = (task: BeadIssue, lastEvent: ActivityEvent | null, pendingRequired: boolean): AgentSessionState => {
+  const deriveState = (
+    task: BeadIssue, 
+    lastEvent: ActivityEvent | null, 
+    pendingRequired: boolean,
+    ownerLiveness?: string
+  ): AgentSessionState => {
     if (task.status === 'closed') return 'completed';
     if (task.status === 'blocked' || pendingRequired) return 'needs_input';
     
-    // Check staleness
+    // If agent is evicted, the task session state is definitely evicted
+    if (ownerLiveness === 'evicted') return 'evicted';
+    if (ownerLiveness === 'stale') return 'stale';
+
+    // Check staleness of the TASK activity itself
     const lastActiveTime = lastEvent ? new Date(lastEvent.timestamp).getTime() : new Date(task.updated_at).getTime();
     if (Date.now() - lastActiveTime > STALE_THRESHOLD_MS) {
       return 'stale';
@@ -172,7 +195,8 @@ export function buildSessionTaskFeed(
     const pendingRequired = taskMessages.some(m => m.requires_ack && m.state !== 'acked');
     const latestMessage = taskMessages.sort((a, b) => b.created_at.localeCompare(a.created_at))[0];
 
-    const sessionState = deriveState(task, lastEvent, pendingRequired);
+    const ownerLiveness = task.assignee ? agentLivenessMap[task.assignee] : undefined;
+    const sessionState = deriveState(task, lastEvent, pendingRequired, ownerLiveness);
 
     const card: SessionTaskCard = {
       id: task.id,