Fix and guard against cross-module export name collisions

[imattau]

Summary

Follow-up to imattau/nscript#3, which fixed the NCC-10/NCC-13 operator_for_tag collision found composing both into examples/service-operator-bot.ns. That fix was ad hoc — nothing checks the whole standard library for this class of bug, only whichever modules one program's own use graph happens to pull in.

• New regression test: built_in_modules_export_no_ambiguous_names_across_the_standard_library (in nscript-modules) replicates nscript-semantics's E4003 ambiguous-export check over every BUILTINS module at once. It found four more real collisions, none previously exercised by any program combining both sides:
  • ncc08.service / ncc09.service → NCC-08's renamed to handover_service
  • ncc00.status / ncc09.status → NCC-09's renamed to authority_status
  • ncc08.state / ncc10.state → NCC-08's renamed to handover_state (coincidentally same name, unrelated signatures/purposes)
  • concord02.Channel / nip28.Channel → concord02's renamed to ConcordChannel
  • concord02.CommunityError / nip72.CommunityError → concord02's renamed to ConcordCommunityError
• Each rename picked whichever side had fewer real call sites to update (concord02 had none outside its own module file). Updated every affected .nsm module, the runtime pure-function registry + its unit tests, the example/conformance scripts calling the renamed functions, and spec/nostr.md/NCC-PLAN.md.
• Documented, not fixed: the other issue building the composite example surfaced — top-level/schedule bodies execute via two independent static passes (literal publishes, then bare operation calls) rather than in source order, so a schedule computing a value and publishing it has to move into a handler instead. Recorded as a follow-up in NCC-PLAN.md; a real fix needs the same sequential, data-flow-aware evaluation a handler body already gets — an evaluator change, out of scope here.

Test plan

• cargo build --workspace — clean
• cargo test --workspace — all tests pass (249 + 69 CLI + 14 nscript-modules tests, including the new guard test)
• cargo fmt --check — clean
• cargo clippy --workspace --tests -- -D warnings — clean
• nscript check on every touched .ns/.nsm file

---

🤖 Generated with Claude Code

https://claude.ai/code/session_01D95PWA2fdNfg7nUvUHBeMi

---

Generated by Claude Code