fix(e2e/copilot): detect trust dialog case-insensitively

Copilot v1.0.63 lowercased the trust-dialog footer from "Enter to select" to "enter to select". StartSession's dismissal loop matched the footer with an exact-case strings.Contains, so the dialog stopped being recognized: the loop saw the dialog's "❯ 1. Yes" selection cursor, mistook it for the interactive prompt, and broke out without pressing Enter. The still-open dialog then swallowed the first real prompt, and every interactive copilot-cli e2e test timed out on WaitFor("❯").

Make isStartupDialog() lowercase-fold the pane and match on the dialog title ("Confirm folder trust" / "Do you trust") as well as the footer, so a future footer-wording change can't silently re-break it. Also widen the WaitFor trigger regex to match the footer case-insensitively.

Adds copilot_trust_test.go with the real v1.0.63 dialog capture as a regression fixture, plus a negative case for the bare prompt.

Fixes the 5 TestInteractive* copilot-cli failures.