fix(security): IPv6 ULA blocking, cookie redaction, per-tab cancel, targeted token (#664)

Community PR #664 by @mr-k-man (security audit round 1, new parts only).

- IPv6 ULA prefix blocking (fc00::/7) in url-validation.ts with false-positive
  guard for hostnames like fd.example.com
- Cookie value redaction for tokens, API keys, JWTs in browse cookies command
- Per-tab cancel files in killAgent() replacing broken global kill-signal
- design/serve.ts: realpathSync upgrade prevents symlink bypass in /api/reload
- extension: targeted getToken handler replaces token-in-health-broadcast
- Supabase migration 003: column-level GRANT restricts anon UPDATE scope
- Telemetry sync: upsert error logging
- 10 new tests for IPv6, cookie redaction, DNS rebinding, path traversal

Co-Authored-By: mr-k-man <mr-k-man@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

browse/src/read-commands.ts

@@ -13,6 +13,10 @@ import * as path from 'path';
 import { TEMP_DIR, isPathWithin } from './platform';
 import { inspectElement, formatInspectorResult, getModificationHistory } from './cdp-inspector';
 
+// Redaction patterns for sensitive cookie/storage values — exported for test coverage
+export const SENSITIVE_COOKIE_NAME = /(^|[_.-])(token|secret|key|password|credential|auth|jwt|session|csrf|sid)($|[_.-])|api.?key/i;
+export const SENSITIVE_COOKIE_VALUE = /^(eyJ|sk-|sk_live_|sk_test_|pk_live_|pk_test_|rk_live_|sk-ant-|ghp_|gho_|github_pat_|xox[bpsa]-|AKIA[A-Z0-9]{16}|AIza|SG\.|Bearer\s|sbp_)/;
+
 /** Detect await keyword, ignoring comments. Accepted risk: await in string literals triggers wrapping (harmless). */
 function hasAwait(code: string): boolean {
   const stripped = code.replace(/\/\/.*$/gm, '').replace(/\/\*[\s\S]*?\*\//g, '');
@@ -300,7 +304,14 @@ export async function handleReadCommand(
 
     case 'cookies': {
       const cookies = await page.context().cookies();
-      return JSON.stringify(cookies, null, 2);
+      // Redact cookie values that look like secrets (consistent with storage redaction)
+      const redacted = cookies.map(c => {
+        if (SENSITIVE_COOKIE_NAME.test(c.name) || SENSITIVE_COOKIE_VALUE.test(c.value)) {
+          return { ...c, value: `[REDACTED — ${c.value.length} chars]` };
+        }
+        return c;
+      });
+      return JSON.stringify(redacted, null, 2);
     }
 
     case 'storage': {