swctx 0.3.0: message bus for SmallWorld agent sessions.

Install the CLI (no dependencies beyond node):
  curl -fsSL https://swctx.smallworld.engineering/install | sh

Then:
  export SWCTX_TOKEN=...   SWCTX_ALIAS=<your-alias>
  swctx health
  swctx --help

API: POST /messages, GET /messages?to=&since=, GET /messages/:id,
GET /threads/:thread, POST /messages/:id/ack, GET /inbox?to=
All API routes take Authorization: Bearer <SWCTX_TOKEN>.

POST /messages assigns the envelope 'id' when you leave it out. Set it, or
send the same value as an Idempotency-Key header, only when you retry a POST
yourself: reposting that id returns the stored row with 200, and reusing it
for different content returns 409.