chore: remove non-functional subagent input feature

Subagents (Task tool background agents) are autonomous and cannot
receive input mid-execution. They complete and return results to
the parent session. Removed the input UI and API endpoint.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test-links.cjs

@@ -0,0 +1,71 @@
+const { chromium } = require('playwright');
+
+(async () => {
+  const browser = await chromium.launch({
+    headless: true,
+    args: ['--ignore-certificate-errors']
+  });
+
+  const context = await browser.newContext({ ignoreHTTPSErrors: true });
+  const page = await context.newPage();
+
+  // Capture console messages
+  const consoleLogs = [];
+  page.on('console', msg => {
+    consoleLogs.push('[' + msg.type() + '] ' + msg.text());
+  });
+
+  console.log('Opening https://localhost:3000...');
+  await page.goto('https://localhost:3000', { waitUntil: 'networkidle' });
+  await page.waitForTimeout(2000);
+
+  console.log('Looking for shell button...');
+  // Click Run Shell button
+  const shellBtn = page.locator('button:has-text("Run Shell")');
+  if (await shellBtn.count() > 0) {
+    await shellBtn.click();
+    console.log('Clicked Run Shell');
+  } else {
+    console.log('Run Shell button not found');
+  }
+
+  await page.waitForTimeout(3000);
+
+  // Type command in terminal
+  console.log('Typing command...');
+  await page.keyboard.type('echo "tail -f /tmp/test.log"');
+  await page.keyboard.press('Enter');
+  await page.waitForTimeout(2000);
+
+  // Take screenshot
+  await page.screenshot({ path: '/tmp/link-test-1.png', fullPage: true });
+  console.log('Screenshot 1 saved');
+
+  // Move mouse over terminal area (approximate coordinates for /tmp/test.log)
+  const terminal = page.locator('.xterm-screen');
+  const box = await terminal.boundingBox();
+  if (box) {
+    console.log('Terminal at: ' + box.x + ', ' + box.y + ', ' + box.width + 'x' + box.height);
+
+    // Move mouse across the area where the path should be (roughly line 2)
+    const y = box.y + 50; // Approximate line 2
+    for (let x = box.x + 50; x < box.x + 300; x += 10) {
+      await page.mouse.move(x, y);
+      await page.waitForTimeout(50);
+    }
+  }
+
+  await page.waitForTimeout(1000);
+  await page.screenshot({ path: '/tmp/link-test-2.png', fullPage: true });
+  console.log('Screenshot 2 saved');
+
+  // Print console logs
+  console.log('\n=== Console Logs ===');
+  consoleLogs.filter(l => l.includes('LinkProvider')).forEach(l => console.log(l));
+
+  // Check if "Found links" appeared
+  const foundLinks = consoleLogs.some(l => l.includes('Found links'));
+  console.log('\nLinks detected:', foundLinks);
+
+  await browser.close();
+})();