`RuntimeGitTarget` carried `connectionId?: string` and no host id, so `undefined`
spelled three different answers at once — "runtime: host", "unresolved", and
"genuinely local". Its sole resolver read `store.getRepo(worktree.repoId)?.connectionId`
and never looked at `worktree.hostId`, which outranks every repo row, so one
arbitrarily chosen row decided the execution host for 36 downstream dispatches.
The target now carries `executionHostId: ExecutionHostId` (never null, never
optional), resolved through the shared rule that landed with #17909/#17919 and
dispatched through the host-keyed routes from #18296. Dispatch sites call
`requireRuntimeGitProvider`, where `null` means exactly one thing: the host is
`local` and the command runs here as free functions.
Four answers that used to collapse into one:
- `ssh:x` with a rival row on `ssh:y` — routes to x. Previously the first row won,
which is the reproduced cross-host leak.
- `local` with a surviving `connectionId` — a row contradicting itself; no SSH
connection is handed out.
- `runtime:<env>` — throws `ExecutionHostNotDispatchableError`. Its repo row's
connection names a target in the *server's* namespace; dialling it here reaches a
same-named target on this client.
- rival rows disagreeing with no worktree host — `worktree_execution_host_unresolved`,
matching the launch path rather than guessing a row.
An unreachable SSH host still throws `SSH_GIT_PROVIDER_UNAVAILABLE_MESSAGE`; loss of
contact is never evidence of locality (docs/reference/ssh-execution-boundary.md).
`resolveWorktreeLaunchHost` keeps its exact signature and now delegates to
`resolveWorktreeHostRouting`, the same resolution answering "which host is this on"
rather than "what may this client dial" — the git target needs the first question
because `local` and `runtime:` are two different non-SSH answers.
No wire change: `RuntimeGitTarget` is main-process internal, and the SSH and local
model-discovery host keys are byte-identical to before.
`RuntimeFileTarget` has the same defect in ~30 filesystem dispatches and is
deliberately left for a follow-up.
Neil