vm run: ship tracked files only by default; add --include-untracked + --dry-run

Workspace-mode vm run and vm workspace prepare used to copy both
tracked AND untracked non-ignored files into the guest. That silently
catches local .env files, scratch notes, credentials, and any other
working-tree state a developer hasn't explicitly gitignored — a real
data-exposure footgun given the golden image ships Docker and the
usual dev tooling.

Flip the default to tracked-only. Users who actually want the fuller
set opt in with --include-untracked (documented in both commands'
help). Gitignored files are still always excluded regardless of the
flag.

Add --dry-run to both vm run and vm workspace prepare. Dry-run
inspects the repo CLI-side (no VM created, no daemon RPC needed since
the daemon is always local and the inspection is a pure git read),
prints the exact file list + mode, and exits. A byte-level preview of
what would land in the guest.

When running real (non-dry) and untracked files exist in the repo but
are being skipped under the new default, print a one-line notice
pointing to --include-untracked so users aren't surprised when the
guest is missing something they expected.

Signature changes:
- ListOverlayPaths takes an includeUntracked bool (tracked always;
  untracked gated by flag).
- InspectRepo takes the same flag and passes it through.
- VMWorkspacePrepareParams gains IncludeUntracked.
- WorkspaceService.workspaceInspectRepo seam signature widened to
  match (4 callers in tests updated).

New workspace package tests cover both modes and verify that
gitignored files never leak regardless of the flag.

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

internal/api/types.go

@@ -137,13 +137,14 @@ type WorkspaceExportResult struct {
 }
 
 type VMWorkspacePrepareParams struct {
-	IDOrName   string `json:"id_or_name"`
-	SourcePath string `json:"source_path"`
-	GuestPath  string `json:"guest_path,omitempty"`
-	Branch     string `json:"branch,omitempty"`
-	From       string `json:"from,omitempty"`
-	Mode       string `json:"mode,omitempty"`
-	ReadOnly   bool   `json:"readonly,omitempty"`
+	IDOrName         string `json:"id_or_name"`
+	SourcePath       string `json:"source_path"`
+	GuestPath        string `json:"guest_path,omitempty"`
+	Branch           string `json:"branch,omitempty"`
+	From             string `json:"from,omitempty"`
+	Mode             string `json:"mode,omitempty"`
+	ReadOnly         bool   `json:"readonly,omitempty"`
+	IncludeUntracked bool   `json:"include_untracked,omitempty"`
 }
 
 type VMWorkspacePrepareResult struct {