Keep material coverage limits separate from outcome claims

Why: A completed run can still lack readable or fully provided source material.

Evidence: Composition validation follows the backend and UI consumers.

Impact: Adds optional host-owned limitations without changing candidate authority.

Refs: fast-slow-u2-u3 Tasks 4 through 6

task_snapshot.go

@@ -74,6 +74,7 @@ type TaskSnapshot struct {
 	NextStep               string            `json:"nextStep,omitempty"`
 	Conclusion             string            `json:"conclusion,omitempty"`
 	Findings               []TaskFinding     `json:"findings,omitempty"`
+	Limitations            []string          `json:"limitations,omitempty"`
 	Inputs                 []TaskSourceRef   `json:"inputs,omitempty"`
 	Actions                []UIAction        `json:"actions,omitempty"`
 	ResultRefs             []TaskResultRef   `json:"resultRefs,omitempty"`

ts/types.ts

@@ -407,6 +407,7 @@ export interface TaskResultRef { artifactId?: ID; surfaceId?: ID; version?: stri
 export interface TaskFinding { id: string; text: string; impact?: string; kind: string; status: string; revision: number; sources: TaskSourceRef[]; assumptions?: string; corrects?: string }
 export interface TaskSnapshot {
 	inputs?: TaskSourceRef[]
+ limitations?: string[]
  schemaVersion: number; taskId: ID; attemptId: ID; cardId: ID; projectId: ID; conversationId: ID;
  sourceMessageId?: ID; parentRunId?: ID; runId?: ID; ownerInstanceId: string; executionEpoch?: number;
  revision: number; sourceSeq: number; streamScope: string; inputRevision?: string; title: string; goal?: string;