fed-sx-m1: Step 7d-pure — sandbox:eval_pure/2,/3 + 13 tests

plans/fed-sx-milestone-1.md

@@ -459,7 +459,7 @@ publish(ActorId, ActivityRequest) ->
 - [x] **7a** — Pure-functional `next/kernel/projection.erl`: `new/2,3`, `fold_activity/2`, `replay/2`, `name/1`, `state/1`, `fold_fn/1`. Projection record is `[{name, _}, {state, _}, {fold, fun}]`; fold body is an Erlang fun in v1 (SX-source eval bridge deferred). `next/tests/projection_pure.sh` (12 cases).
 - [x] **7b** — gen_server-per-projection: `start_link/3(Name, InitialState, FoldFn)` + `async_fold/2(Name, Activity)` (cast) + `query/1(Name)` (call) + `stop/1`. Each projection registered under its own Name atom. `next/tests/projection_server.sh` (11 cases). Snapshot persistence deferred (needs SX-source eval + on-disk state).
 - [x] **7c** — `outbox:publish` broadcast hook: after `log:append`, fans out the signed activity to every projection listed under `Context`'s `:projections` entry via `projection:async_fold`. Stage halts (replay, sig failure) skip broadcast. `next/tests/outbox_broadcast.sh` (14 cases).
-- [ ] **7d** — `sandbox:eval_pure/2` (Erlang sandbox-mode caller — gas budget + IO denial) once an SX-source eval bridge exists.
+- [x] **7d-pure** — `next/kernel/sandbox.erl` with `eval_pure/2` and `eval_pure/3` — try/catch wrappers over Erlang funs. Catches throw, error, exit; returns `{ok, Result}` on success, `{error, {Class, Reason}}` on exception. Gas/IO sandboxing lands with SX-source eval; API shape is stable. `next/tests/sandbox_eval.sh` (13 cases).
 
 **Deliverables:**
 
@@ -1002,6 +1002,7 @@ A few things still under-specified; resolve as work begins.
 Newest first. One line per sub-deliverable commit. Erlang conformance gate
 (`bash lib/erlang/conformance.sh`) must remain 729/729 on every entry.
 
+- **2026-05-28** — Step 7d-pure: `next/kernel/sandbox.erl` — `eval_pure/2(Fun, Arg)` and `eval_pure/3(Fun, Activity, State)`. try/catch envelope returns `{ok, Result}` on success and `{error, {Class, Reason}}` for each of the three exception classes (throw, error, exit). The 3-arity variant matches the projection-fold shape so the scheduler can wrap fold bodies. Port note: this Erlang implementation catches by explicit class names rather than the open `Class:Reason` pattern — wrappers enumerate `throw:Reason / error:Reason / exit:Reason` explicitly. Real gas budget + IO denial + env-stripping lands with SX-source eval; the wrapper API doesn't change. `next/tests/sandbox_eval.sh` 13/13. Erlang conformance 729/729.
 - **2026-05-28** — Step 9b-pure: **reactive application extensibility, proven end-to-end.** Mirrors §Step 9b structurally without TCP/curl/JSON. A trigger projection (Erlang-fun fold over `{Captured, Count}` state) matches Note activities whose `:object :tags` contains `smoketest`, constructs a derived `TestEcho` activity with `:object :echoes` pointing at the Note's `:id`, and captures it into projection state. Order-independent; non-Note + non-smoketest + Note-without-tags + sig-failed publishes all suppressed correctly. Multi-tag (e.g. `[smoketest, foo, bar]`) still matches. Cascade publish (the trigger actually publishing the derived activity back through outbox) is deferred — the gen_server reentrancy that introduces is a v2 concern; the projection-state capture is sufficient proof of the match-then-derive mechanism. `next/tests/smoke_app_pure.sh` 12/12. Erlang conformance 729/729.
 - **2026-05-28** — Step 9a-pure: **the first verb-extensibility smoke test, proven end-to-end.** Mirrors §Step 9a structurally without TCP/curl/JSON. Two projections wired into `nx_kernel:with_projections([define_reg, pin_state])` — `define_reg` uses `define_registry:fold_fn/0` (Step 5d-pure), `pin_state` uses an Erlang-fun fold that records `{Path, Cid}` from Pin activities. Publish `Create{DefineActivity{name: pin}}` → registry update visible via `registry:lookup(activity_types, pin, projection:query(define_reg))`; publish `Pin{path: docs_intro, cid: qm_cid_1}` → `projection:query(pin_state) =:= [{docs_intro, qm_cid_1}]`. Order-independent (DefineActivity-then-Pin and Pin-then-DefineActivity both succeed); Note + non-Define types are pass-throughs in both projections. The TCP/curl variant (Step 9a-tcp) layers on Step 8b-start. `next/tests/smoke_pin_pure.sh` 13/13. Erlang conformance 729/729.
 - **2026-05-28** — Step 5d-pure: `next/kernel/define_registry.erl` — the meta-projection fold body, in pure Erlang. State shape mirrors `registry:new()` exactly; `fold/2` dispatches Create{Define*} to `registry:register/4` keyed by `define_kind/1` (define_activity → activity_types, define_object → object_types, …). Non-Create + Create{non-Define} + Define{no :name} are all pass-throughs. Override re-registration preserves a single entry per name. `fold_fn/0` plugs the fold into `projection:start_link/3` — verified end-to-end: activity → projection async_fold → query state → registry:lookup returns the registered Object. The SX `define-registry.sx` body will replace this once an SX-source eval bridge exists; the Erlang shape proves the wiring is correct. `next/tests/define_registry_pure.sh` 16/16. Erlang conformance 729/729.