Spawn receipt fixtures (schema v1)

Cross-language contract for realtime spawn_agent results:

• Producer: desktop/macos/agent/src/runtime/agent-spawn-journal.ts → compactRealtimeSpawnToolResult
• Consumer: Swift RealtimeSpawnJournalReceipt.parse (currently in RealtimeHubController.swift)

Rules

• v1/ fixtures are immutable. Never edit a checked-in v1 JSON file to “fix” a test; add a new fixture or open a v2 directory.
• Adding schema 2 means creating ../v2/ with its own valid + malformed set; keep v1 until the producer stops emitting it.
• Tests compare decoded semantic values, not byte-identical JSON (key order / whitespace are not protocol).

Files

File	Expectation
valid-running.json	Swift parse accepts; Node emitter must match semantically for the same descriptor
malformed-*.json	Swift parse returns nil without crashing