Context

Existing configs may have default: true on agent entries. This field has no meaning post-gut but must be handled gracefully for backward compatibility.

Depends on #1575 (schema field removal).

What

1. Ensure zod schema strips default field silently on load (no parse error)
2. remoteclaw doctor warns when default: true found in raw config
3. materializeWorkspaceDefaults() in import command strips the field
4. Config merge-patch ignores/strips the field

Acceptance Criteria

• Config with default: true loads without parse error (field silently stripped)
• remoteclaw doctor warns about deprecated default field with removal guidance
• Import command strips default field from materialized output
• Config merge-patch handles default field gracefully
• Tests updated; CI passes

Files

• src/config/zod-schema.agent-runtime.ts — currently ACCEPTS default: true at line 692 (does not strip it); this issue should add strip/ignore behavior so the field is silently dropped on parse
• src/commands/import.ts (materializeWorkspaceDefaults)
• src/config/validation.ts (deprecation warning)
• src/agents/agent-scope.ts — the PRIMARY consumer of default: true (via resolveDefaultAgentId at line 70 which reads agent?.default)
• src/config/legacy.shared.ts — resolveDefaultAgentIdFromRaw at line 94 reads entry.default === true