guest.session.send — write to a pipe-mode session's stdin without
holding the exclusive attach. The daemon dials a fresh SSH connection,
uploads the payload to a temp file, and cats it into the session's
named FIFO. Linux atomicity for writes ≤ PIPE_BUF covers all pi RPC
JSONL lines. Attach exclusivity is unchanged.
vm.workspace.export — pull changes from guest back to host. Runs
`git add -A && git diff --cached HEAD --binary` inside the guest via a
new RunScriptOutput helper on guest.Client (stdout-only capture,
distinct from RunScript which merges stderr). Returns a binary-safe
patch and a list of changed files. CLI writes the patch to stdout for
`| git apply` or to a file via --output.
RunScriptOutput is implemented as a direct SSH session (same pattern as
runSession) rather than going through StartCommand/StreamSession to
avoid closing the underlying Client, which is required since
ExportVMWorkspace calls it twice on the same connection.
New files: internal/daemon/workspace_test.go
Guest session cwd and command preflight helpers were emitting literal
`\\n` separators, so the guest shell saw malformed one-line scripts and
could fail `preflight_cwd` even when `/root/repo` already existed.
Replace those builders with real newlines, and fix the nearby attach
helper commands that were making the same mistake.
Add a small daemon guest-SSH seam so workspace preparation and session
start can share a fake backend in tests, then cover the regression with
an end-to-end daemon test for `PrepareVMWorkspace` followed by
`StartGuestSession` on `/root/repo`.
Validation: `GOCACHE=/tmp/banger-gocache go test ./internal/daemon` and
`GOCACHE=/tmp/banger-gocache go test ./...`.
