Pace candidate funnel to send capacity

tests/candidate-queue.test.ts

@@ -77,10 +77,23 @@ describe('CandidateQueueRepository', () => {
       duplicateAuthor: 1,
       previouslyProcessed: 0,
       previouslyContacted: 0,
+      deferredAtCapacity: 0,
     });
     expect(queue.getStats().byStatus.discovered).toBe(2);
   });
 
+  it('fills only the requested intake deficit and reports untouched posts', () => {
+    const result = queue.enqueue([
+      post('p1', 'alice'),
+      post('p2', 'bob'),
+      post('p3', 'carol'),
+    ], 'image', 1, 1_000, 2);
+
+    expect(result.discovered).toBe(2);
+    expect(result.deferredAtCapacity).toBe(1);
+    expect(queue.countActive()).toBe(2);
+  });
+
   it('excludes posts and recipients already handled anywhere', () => {
     db.prepare(`
       INSERT INTO processed_posts (account_id, id, subreddit, author, title, processed_at)

tests/main-loop.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, it, vi } from 'vitest';
-import { currentHourlySendCount, startNonOverlappingSchedule } from '../src/main-loop.js';
+import {
+  calculateCandidateFunnelTarget,
+  currentHourlySendCount,
+  startNonOverlappingSchedule,
+} from '../src/main-loop.js';
 
 describe('startNonOverlappingSchedule', () => {
   it('does not begin a second response check until the prior check settles', async () => {
@@ -43,3 +47,29 @@ describe('currentHourlySendCount', () => {
     expect(currentHourlySendCount({ getStats: () => ({ messagesThisHour: 1 }) })).toBe(1);
   });
 });
+
+describe('calculateCandidateFunnelTarget', () => {
+  it('tracks remaining outbound capacity instead of growing to a fixed backlog', () => {
+    expect(calculateCandidateFunnelTarget(
+      [{ messagesRemaining: 3 }, { messagesRemaining: 5 }],
+      { maxReadyCandidates: 25, recentWindowMinutes: 60, minDelayBetweenMessagesMs: 300_000 },
+    )).toBe(8);
+  });
+
+  it('retains the configured ceiling and caps capacity by the freshness window', () => {
+    expect(calculateCandidateFunnelTarget(
+      [{ messagesRemaining: 100 }, { messagesRemaining: 100 }],
+      { maxReadyCandidates: 25, recentWindowMinutes: 30, minDelayBetweenMessagesMs: 300_000 },
+    )).toBe(12);
+  });
+
+  it('stops growing inventory when no running account can send', () => {
+    const options = {
+      maxReadyCandidates: 25,
+      recentWindowMinutes: 60,
+      minDelayBetweenMessagesMs: 300_000,
+    };
+    expect(calculateCandidateFunnelTarget([], options)).toBe(0);
+    expect(calculateCandidateFunnelTarget([{ messagesRemaining: 0 }], options)).toBe(0);
+  });
+});