opstate,daemon: list in-flight operations via daemon.operations.list

Prerequisite for `banger update`'s preflight, which refuses to swap
binaries while anything is in flight. Today's opstate.Registry
exposes Insert/Get/Prune but no iteration; without a snapshot
accessor the update flow can't tell whether a vm.create is
mid-prepare-work-disk.

  * opstate.Registry.List(): returns a freshly-allocated snapshot
    of every entry. Mutating the slice doesn't poison the
    registry. Pinned by tests covering the snapshot semantics
    and the empty case.
  * api.OperationSummary / OperationsListResult: a public-shape
    record per op. Today the Kind is always "vm.create" — the
    field exists so future async kinds (image.pull, kernel.pull)
    plug in without an API change.
  * Daemon.ListOperations + daemon.operations.list RPC:
    walks vmService.createOps and emits OperationSummary entries.
    Done ops are included in the snapshot; the update preflight
    filters by Done itself.
  * dispatch_test's documented-methods list updated.

No behaviour change for existing flows; this is a read-only
addition.

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

internal/api/types.go

@@ -174,6 +174,20 @@ type ImageRefParams struct {
 	IDOrName string `json:"id_or_name"`
 }
 
+type OperationSummary struct {
+	ID        string    `json:"id"`
+	Kind      string    `json:"kind"`
+	Stage     string    `json:"stage,omitempty"`
+	Detail    string    `json:"detail,omitempty"`
+	Done      bool      `json:"done"`
+	StartedAt time.Time `json:"started_at,omitempty"`
+	UpdatedAt time.Time `json:"updated_at,omitempty"`
+}
+
+type OperationsListResult struct {
+	Operations []OperationSummary `json:"operations"`
+}
+
 type ImageCachePruneParams struct {
 	DryRun bool `json:"dry_run,omitempty"`
 }