Start-Copilot: add first-class -AssistedApproval mapping for copilot --assisted-approval

[shmuelie]

Summary

Start-Copilot maps most of the Copilot CLI's launch flags to first-class parameters, but not --assisted-approval. Today it is only reachable via the -RemainingArgs passthrough, so it has no dedicated switch, help, tab-completion, or validation — unlike the rest of the wrapped surface.

Feature

copilot --assisted-approval reviews tool-permission requests with the assisted-approval safety judge instead of approving them outright (equivalent to the assisted mode of /permissions). Per the CLI help it takes precedence over --allow-all-tools when the judge engages, and it requires experimental mode (--experimental / the AUTO_APPROVAL feature flag).

Observed on GitHub Copilot CLI 1.0.81.

Proposal / acceptance criteria

• Add a first-class -AssistedApproval switch to Start-Copilot that emits --assisted-approval.
• Handle/document the interaction with the launcher's default --allow-all: the judge takes precedence over allow-all-tools, and the flag needs experimental mode (which Start-Copilot enables by default, so it is compatible unless -NoExperimental is set — document that combination).
• Comment-based help, README, and an [Unreleased] CHANGELOG.md entry.
• Tests asserting the flag is emitted and composes correctly with the default permission/experimental flags.