checkpoint NDJSON: match real Sprites {type, data, time} shape

[lex00]

What

Real api.sprites.dev streams checkpoint create/restore progress as {"type","data","time"} NDJSON lines with no structured id field — the version id rides in the message text ( ID: v1, Checkpoint v1 created successfully). spritzer emitted the older {event, message, id} shape, so a client that faithfully mines the id from the text got nothing back from the emulator.

Changes

• progressEvent is now {type, data, time}; create and restore emit the real message lines, stamped with the server clock.
• Test helper mines the id from the message text (mirroring a real client).

Validation

• go build, go vet, go test ./... all pass.
• Ran the binary and diffed the wire output against api.sprites.dev — faithful on the id-bearing lines:

  {"type":"info","data":"Creating checkpoint...","time":...}
  {"type":"info","data":"Checkpoint created successfully",...}
  {"type":"info","data":"  ID: v1",...}
  {"type":"info","data":"  Path: checkpoints/v1",...}
  {"type":"complete","data":"Checkpoint v1 created successfully",...}
  

Downstream: the chant temporal lexicon's parseCheckpointNdjson already reads the id from this text, verified against live Sprites.