feat(soroban): make registry optional in example-compliant-token

[alex-predicate]

What

Make the registry optional in example-compliant-token so the token can be deployed on a network that has no PredicateRegistry yet (e.g. Stellar mainnet today), while keeping the compliance guarantee that the token never performs an unchecked transfer.

Changes (soroban/example-compliant-token/src/lib.rs)

• __constructor registry is now Option<Address> — omit --registry on the CLI to deploy without one.
• New admin-only set_registry(registry) to attach (or replace) a registry later.
• New TokenError::RegistryNotConfigured. register_policy (now returns Result) and transfer return it when no registry is set. transfer checks before moving any tokens — fail-safe, never an unchecked transfer.
• registry() getter now returns Option<Address>.
• Added test_no_registry_placeholder covering the deploy-without-registry → mint/balance → attach-registry flow.

Behavior with no registry

mint / balance / policy_id / deploy all work. The policy_id string is stored but inert until a registry is attached and register_policy succeeds. transfer and register_policy return RegistryNotConfigured.

Testing

• cargo test -p example-compliant-token — 3/3 pass (watched the new test fail first).
• cargo clippy -p example-compliant-token — clean.
• stellar contract build --package example-compliant-token — builds for wasm32v1-none.

Deployed

Deployed to Stellar mainnet as a registry-less placeholder with policy x-managed-policy-2f0e79710e5254bdf4a978c49907b114:
CAYXGYBS2EZROB6MEA6EO7BOP4JDD7R6W3HW3VIFPDYODRUXI4EMXER7

🤖 Generated with Claude Code

[cursor]

Bugbot is not enabled for this team, so this pull request was not reviewed.

Enable Bugbot in the Cursor dashboard to get automatic reviews on future PRs.