Fix cursor / gemini E2E harness issues

[Soph]

this is a slimmed down version of #908

It only keeps the E2E harness related fixes, the other fix regarding condension we should handle separate later

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Note

Medium Risk
Moderate risk because it changes E2E session synchronization and writes a Gemini acknowledgments file in the user home directory, which could affect parallel runs or local environments if the format/paths differ.

Overview
Improves E2E reliability for Cursor and Gemini CLI agents by broadening prompt/startup dialog detection to handle newer UI copy and additional onboarding modals.

For Gemini E2E repos, SetupRepo now proactively records an acknowledgment for the generated entire-search agent by hashing the agent file and updating ~/.gemini/acknowledgments/agents.json under a mutex to avoid interactive “acknowledge and enable” blocks during tests.

^{Reviewed by Cursor Bugbot for commit 7aecd3f. Configure here.}

[Copilot]

Pull request overview

Updates the E2E harness to better tolerate upstream TUI/UX changes in Cursor and Gemini CLIs, reducing startup-related flakes in CI while keeping the core product code unchanged.

Changes:

• Pre-acknowledge the repo-managed Gemini entire-search agent during E2E repo setup by writing a hash entry into Gemini’s acknowledgments file.
• Expand Gemini interactive startup dialog detection to include new “agent discovered” prompts.
• Broaden Cursor CLI prompt readiness detection to match both legacy and current placeholder text.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
e2e/testutil/repo.go	Adds Gemini acknowledgments seeding during repo setup to avoid discovery prompts blocking startup.
e2e/agents/gemini.go	Expands startup prompt regex to recognize new Gemini dialogs.
e2e/agents/cursor_cli.go	Updates prompt regex to handle multiple Cursor CLI placeholder variants.

[Soph]

Addressing the comments in a follow up PR.