seams: move the last four package globals onto instance fields

Three test seams were still package-level mutable vars, which tests
had to swap before use. That's the classic path to flaky parallel
tests — two goroutines fighting over the same global fake. Push each
down to the struct that owns the behaviour.

internal/daemon/dns_routing.go
  lookupExecutableFunc + vmDNSAddrFunc → fields on *HostNetwork,
  defaulted at newHostNetwork time. dns_routing_test builds
  HostNetwork{..., lookupExecutable: stub, vmDNSAddr: stub} inline,
  no more t.Cleanup dance around package-level vars.

internal/daemon/preflight.go + doctor.go
  vsockHostDevicePath (mutable string) → vsockHostDevice field on
  *VMService, defaulted via defaultVsockHostDevice constant in
  newVMService. Preflight reads s.vsockHostDevice; doctor reads
  d.vm.vsockHostDevice. Logger test sets d.vm.vsockHostDevice = tmp
  after wireServices.

internal/daemon/workspace/workspace.go
  HostCommandOutputFunc → *Inspector struct with a Runner field.
  Every git-using helper (GitOutput, GitTrimmedOutput,
  GitResolvedConfigValue, RunHostCommand, ListSubmodules,
  ListOverlayPaths, CountUntrackedPaths, InspectRepo,
  ImportRepoToGuest, PrepareRepoCopy) is now a method on *Inspector.
  NewInspector() wraps the real host runner for production;
  WorkspaceService holds one via repoInspector, CLI deps holds one
  too. cli_test.go's submodule-rejection test builds its own
  Inspector with a scripted Runner instead of patching a global.
  Pure helpers (FinalizeScript, ResolveSourcePath, ParsePrepareMode,
  ShellQuote, FormatStepError, GitFileURL, ParseNullSeparatedOutput)
  stay free functions since they don't touch the host.

Sentinel: grep for HostCommandOutputFunc, lookupExecutableFunc,
vmDNSAddrFunc, vsockHostDevicePath is now empty across internal/.
make lint test green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/daemon/vm_service.go

@@ -66,6 +66,11 @@ type VMService struct {
 	// Test seams.
 	guestWaitForSSH func(context.Context, string, string, time.Duration) error
 	guestDial       func(context.Context, string, string) (guestSSHClient, error)
+	// vsockHostDevice is the path preflight + doctor expect to find for
+	// the vhost-vsock device. Defaults to defaultVsockHostDevice; tests
+	// point at a tempfile so RequireFile passes without needing the
+	// real kernel module loaded.
+	vsockHostDevice string
 
 	// Capability hook dispatch. VMService invokes capabilities via
 	// these seams, populated by Daemon.buildCapabilityHooks() at
@@ -104,9 +109,14 @@ type vmServiceDeps struct {
 	guestDial       func(context.Context, string, string) (guestSSHClient, error)
 	capHooks        capabilityHooks
 	beginOperation  func(name string, attrs ...any) *operationLog
+	vsockHostDevice string
 }
 
 func newVMService(deps vmServiceDeps) *VMService {
+	vsockPath := deps.vsockHostDevice
+	if vsockPath == "" {
+		vsockPath = defaultVsockHostDevice
+	}
 	return &VMService{
 		runner:          deps.runner,
 		logger:          deps.logger,
@@ -120,6 +130,7 @@ func newVMService(deps vmServiceDeps) *VMService {
 		guestDial:       deps.guestDial,
 		capHooks:        deps.capHooks,
 		beginOperation:  deps.beginOperation,
+		vsockHostDevice: vsockPath,
 		handles:         newHandleCache(),
 	}
 }