more hermetic separation for gemini auth config files in E2E

[Soph]

Entire-Checkpoint: 58a364f11b5f

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Note

Low Risk
Low risk and test-only, but it changes how gemini is bootstrapped and which HOME/acknowledgment files it reads, so Gemini E2E runs could fail if the CLI expects additional state in the real home directory.

Overview
Makes Gemini E2E runs hermetic by isolating Gemini CLI state into a per-repo test HOME directory. The Gemini agent no longer writes global auth config in Bootstrap; instead, SetupRepo creates a dedicated ...-gemini-home directory, seeds .gemini/settings.json, and writes acknowledgment state there.

Gemini prompt and interactive session execution now explicitly set HOME to this test directory (and preserve TERM for tmux runs), removing previous reliance on the developer’s real home directory and eliminating the prior global mutex/serialization around acknowledgments. Adds a standalone docs/gmeta-poc-plan.md planning document (no production code changes).

^{Reviewed by Cursor Bugbot for commit f7f3d0d. Configure here.}

[Copilot]

Pull request overview

This PR aims to make Gemini E2E runs more hermetic by moving Gemini auth/settings/acknowledgment files out of the real user home directory and into a per-test isolated HOME, reducing cross-test and developer-environment interference.

Changes:

• Create and populate a per-repo “Gemini test HOME” directory (settings + acknowledgments) during E2E repo setup.
• Stop writing Gemini settings into the real ~/.gemini during agent bootstrap and instead run Gemini with HOME pointed at the test-specific directory.
• Add a new docs/gmeta-poc-plan.md document (appears unrelated to the PR title/purpose).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
e2e/testutil/repo.go	Creates an isolated Gemini HOME dir per test repo and writes Gemini settings/acknowledgments there.
e2e/agents/gemini.go	Stops global bootstrap config writes; sets HOME for Gemini subprocesses and tmux sessions to the isolated directory.
docs/gmeta-poc-plan.md	Adds a gmeta POC plan document (scope seems separate from Gemini E2E hermeticity).