Retain failed-attempt diagnostics and bound account setup

[dnlbui]

What Changed

Failed setup and lookup attempts now retain the evidence needed to distinguish client, gateway, and test failures.

• Retain traces from every failed attempt, including attempt zero, and capture recipient pages before cleanup.
• Record public account identity, request timing, gateway URLs, HTTP/transport outcomes, relevant sanitized responses, and console/page errors across custom contexts and popups.
• Bound account setup to 90 seconds, require the expected signed-in account, and report the failing stage. Recipient lookup waits up to ten seconds for the existing UI result instead of sleeping three seconds.
• Preserve the original setup/assertion failure when cleanup also fails. Add an offline diagnostic harness and artifact verifier.

Fixed Flow

1. Observe account setup or recipient lookup before requests begin.
2. Wait for the expected UI state within a defined deadline.
3. On failure, capture the affected page and network evidence before closing it.
4. Retain that attempt's artifacts even if a fresh retry later succeeds.

Why

The original CI failures could not distinguish unavailable registration receipts, delayed username availability, transport errors, or negative lookup responses. First-attempt traces were lost, and cleanup could hide the failing page. These changes improve failure reporting without automatically retrying registration or accepting an incorrect lookup result.

The application recovery defect is addressed separately in web-client-v2 #1744.

Validation

Rebase verification (October 5, 2026): git range-diff confirms the diagnostics patch is unchanged. Both multi-user tests passed against /dev with two workers and retries disabled, including the inherited reply-toll fix. npm run test:diagnostics again verified all nine cases and the retained artifacts from the two deliberate first-attempt failures.

• Six live smoke tests against https://liberdus.com/dev/ passed with retries disabled.
• Focused live transfer test passed with retries disabled.
• npm run test:diagnostics: nine offline cases verified; two deliberately fail their first attempt to verify retained artifacts after a successful retry.
• JavaScript syntax and git diff --check passed.
• Separate make-code-skimmable review completed.

Stacked on #87 (reply-toll timing fix); review this PR against test/reply-within-toll-window, which is based on #83. The diagnostics changes are unchanged by this rebase.

Closes #78

[dnlbui]

closing for now until we decide to merge this in since this is a larger PR.