feat(code): multi-repo support for cloud tasks

[adboio]

Problem

it's not intuitive to have a cloud task work across more than one repo

backend sandbox PR: PostHog/posthog#68673

Changes

this PR only solves the "start a cloud task with >1 repos" problem. multi-PR support & UX in future PRs!

• adds new multi-repo selector UX to new cloud task input (mirroring local)
• updates cloud system prompt to include additional repos (mirroring local) and accept additional repos in AgentServerConfig

How did you test this?

manually

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

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[adboio]

• feat(code): multi-repo support for cloud tasks #3184 👈 (View in Graphite)
• main

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[greptile-apps]

_{Reviews (1): Last reviewed commit: "feat(code): multi-repo support for cloud..." | Re-trigger Greptile}

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit e2f3713.}

[greptile-apps]

_{Reviews (2): Last reviewed commit: "feat(code): multi-repo support for cloud..." | Re-trigger Greptile}