fix(runtime): redact URL userinfo in command results - #21

Bug and impact

Playwright preserves URL userinfo (user:password@host) on page.url() and resolved HTMLAnchorElement.href. Companion/MCP forwarded those strings in navigate/click/type url, snapshot url / htmlSnippet / links[].href, and COMMAND_FAILED messages.

That leaks basic-auth credentials into agent tool output and logs. Distinct from PR #18 (password form fields in ariaSnapshot/page.content) and from PRs #16/#20 (navigate/click SSRF allowlists).

Trigger

1. navigate to https://user:SECRET@example.com/, then read the command result url or a following snapshot.url.
2. snapshot a page whose anchors resolve to https://user:SECRET@… — secret appears in links[].href and htmlSnippet.
3. A failed goto whose Playwright message embeds the credentialed URL.

Live Chromium on HEAD a0fabe3 reproduced (1) and (2) before this change.

Fix

• Strip userinfo from emitted URLs and free-form snapshot text (packages/runtime/src/url-redact.ts).
• Omit data: payloads from page.url() so percent-encoded hrefs cannot hide credentials in snapshot.url.
• Redact userinfo in mapCommandFailure messages.
• Navigate with userinfo still works for HTTP basic auth; only client-visible results are scrubbed.

Tests

• packages/runtime/src/url-redact.test.ts
• Runtime mock test for navigate/snapshot outputs
• mapCommandFailure userinfo case
• pnpm --filter @webchain/runtime test:coverage (line coverage 94.36%, threshold 90) and live Chromium re-probe after the fix