Extract vzy into its own reusable VM-scripting repository; convert the research branches' automation into vzy scripts

[obj-p]

Decision (owner, 2026-07-10, revised)

The local VM merge queue is retired in favor of CI (#364). vzy/ survives as its own project: a generic, reusable VM scripting repository. The research work does NOT migrate into that repo.

Scope

• Create the new repository and move vzy/ there, preserving history (git subtree split / git filter-repo on the vzy/ path — note main and branches diverge: the kit evolved on mergequeue-vz-kit and the research branches; salvage the newest kit code before Decommission the in-tree merge queue once CI is proven (remove merge-queue/, devbox/, vzy/; close #230 and follow-ups) #364 deletes the branch).
• The new repo carries ONLY the reusable kit (boot/snapshot/install/setup, screen-dispatch SA engine, SSH provisioning, dir sharing). Design constraint stands: no PreviewsMCP-specific coupling.
• The research branches STAY on PreviewsMCP. Their research/vm automation gets converted into scripts that consume vzy (the kit's consumer-plan model), replacing the in-branch copies of kit code.
• PreviewsMCP-side removal of vzy/ from main is tracked in Decommission the in-tree merge queue once CI is proven (remove merge-queue/, devbox/, vzy/; close #230 and follow-ups) #364.

Context

• The vz kit + bar landed via Local merge queue: vzy VM kit + Bazel in-VM merge bar (#230) #261; the real merge-queue cutover never happened, so no GitHub-side authority is involved.
• Local key material and VM caches were already deleted on 2026-07-10.

[obj-p]

vzy extracted to its own repository: https://github.com/obj-p/vzy

Split source: local ios-e2e-deflake @ 6d7e0ec, not origin/mergequeue-vz-kit. Verification before splitting showed the deflake branch carries the newest kit code, a strict content superset of mergequeue-vz-kit's vzy/: it adds the stale-VM-reaper teardown in Guest.swift (f50d450, unpushed, salvaged partially to main via #319), the non-blocking RFB connect with reconnect socket-leak fix, and the host() drain-with-error-capture. Nothing unique to mergequeue-vz-kit's tree was lost (diff checked file by file). Both refs carry the same 7-commit vzy/ history depth.

Extracted via git subtree split --prefix=vzy in a temp clone, pushed as main (7 commits, head 836b466). The new repo root tree exactly matches ios-e2e-deflake:vzy (empty diff). Tree shape verified: Sources/VZKit (20 entries), Sources/VZKitObjC, Sources/vzy, Package.swift, build.sh, Resources.

Converting the research branches' research/vm automation into vzy-consumer scripts remains future work per this issue. Removal of vzy/ from PreviewsMCP main stays deferred to #364 until this repo is verified.