catalogue: publish Smol Machines (io.pilot.smolmachines v1.2.0) [needs re-sign]

[Alexgodoroja]

Publish Smol Machines (io.pilot.smolmachines v1.2.0)

Adds the catalogue entry + rich metadata that lists Smol Machines (the smolvm
microVM engine) in the app store. Bundles are hosted in the Pilot R2 artifact
registry (pilot-artifacts-prod); all four platforms (darwin/linux × amd64/arm64).

• catalogue/catalogue.json — entry appended (existing 3 apps untouched). Short
  description → pilotctl appstore list.
• catalogue/apps/io.pilot.smolmachines/metadata.json — long description_md →
  pilotctl appstore view; passthrough smolmachines.exec with the full smolvm
  command surface baked into its help (no enumerated methods).

Verified locally end-to-end: catalogue → pilotctl appstore install io.pilot.smolmachines
→ adapter stages the binary from R2 → pilotctl appstore call ... smolmachines.exec
boots a real Alpine microVM.

⛔ Blocking: re-sign before merge (needs the release key)

catalogue.json changed, so catalogue/catalogue.json.sig is now stale. pilotctl
and the daemon verify the detached signature against the embedded catalogue
public key (internal/catalogtrust), so an unsigned/stale catalogue is rejected on
every host. The private key is not in the repo (confirmed — it's the
CATALOG_SIGN_KEY release secret / offline key). A key-holder must regenerate the
signature before merge:

# with the release private key (hex-encoded 64-byte ed25519, the CATALOG_SIGN_KEY value)
pilotctl appstore sign-catalogue --key /secure/path/catalog-signing.key catalogue/catalogue.json
git add catalogue/catalogue.json.sig && git commit -m "catalogue: re-sign" && git push

(Or drive it through the app-template publish-on-merge automation, which signs with
the CATALOG_SIGN_KEY secret.)

Depends on

The app only installs/runs once the daemon is on the proc.exec version with the
install-spec + trust-anchor wiring: app-store#24, pilotprotocol#317, pilotprotocol#318.
The listing itself (this PR) is independent.

🤖 Generated with Claude Code