pi-v0.4.0

Publish the Pi source already merged into Engram main, including replay-safe native mem_save recovery. Align installer metadata and migrate existing gentle-engram 0.3.0 pins idempotently while preserving unrelated settings and MCP configuration.

Install:
```sh
pi install npm:gentle-engram@0.4.0
pi-engram init
```

Released Engram core 3.3.0 still pins Pi 0.3.0 through built-in setup; use the explicit install above for this package.

Verification: 355 Pi tests, Go setup package, independent verification, native review and PR CI passed. Published npm metadata and tarball availability verified; npm gitHead matches the release tag and merge commit.

Release preparation: #1740 (issue #1738).