fed-sx-m1: Step 7b — gen_server-per-projection (start_link/3 + async_fold + query) + 11 tests

plans/fed-sx-milestone-1.md

@@ -457,7 +457,7 @@ publish(ActorId, ActivityRequest) ->
 
 **Sub-deliverables:**
 - [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).
-- [ ] **7b** — gen_server wrapper: `start_link/1`, named-per-projection, `async_fold/2`, `query/1`, `snapshot/1`.
+- [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).
 - [ ] **7c** — Broadcast hook from `outbox:publish` — feed `Signed` to every projection process.
 - [ ] **7d** — `sandbox:eval_pure/2` (Erlang sandbox-mode caller — gas budget + IO denial) once an SX-source eval bridge exists.
 
@@ -977,6 +977,7 @@ 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 7b: `projection.erl` extended with gen_server callbacks + per-projection named-process API. `start_link/3(Name, InitialState, FoldFn)` spawns and registers under the supplied atom; `async_fold/2(Name, Activity)` casts a fold message; `query/1(Name)` synchronously returns the current state. Same port quirks as registry gen_server (Step 5b): raw Pid return, no `?MODULE` macro, processes don't survive between separate `erlang-eval-ast` calls — tests inline start_link with operations. Two named projections are independent. Snapshot persistence deferred to a later sub-step (needs SX-source eval + on-disk state). `next/tests/projection_server.sh` 11/11. Erlang conformance 729/729.
 - **2026-05-28** — Step 7a: `next/kernel/projection.erl` — pure-functional projection driver. Record shape `[{name, _}, {state, _}, {fold, fun}]`; `fold_activity/2` advances state by one activity; `replay/2` folds a whole list (mirrors `log:entries/1` semantics); `new/2` defaults to the identity fold and `new/3` accepts a custom Erlang fun. Multiple projections share no state — independent record values. Step 7 split into 7a (done) + 7b (gen_server-per-projection) + 7c (broadcast hook from outbox) + 7d (sandbox eval, needs SX-source bridge). `next/tests/projection_pure.sh` 12/12. Erlang conformance 729/729.
 - **2026-05-28** — Step 6d-publish: `outbox:publish/2(Request, Context)` orchestrates construct + sign + `pipeline:run_stages` + `log:append`. Stage list is `[stage_envelope, stage_signature(AS), stage_replay(LogState)]` — so a duplicate publish (same Request, same Published) halts at the replay stage and returns `{error, replay, LogState}` with the log unchanged; bad key material halts at `bad_signature`. Happy path returns `{ok, [{cid, Cid}, {activity, Signed}], NewLog}`. Projection-scheduler dispatch deferred to Step 7. `next/tests/outbox_publish.sh` 13/13 covers happy path, replay halt, sig halt, multi-publish progression, CID stability across fresh logs. Erlang conformance 729/729.
 - **2026-05-28** — Step 6d-cs: `next/kernel/outbox.erl` — envelope construction + signing. `construct/4` takes `(Type, ActorId, Published, Object)`, builds the canonical key-sorted property list, and derives the activity `:id` from `cid:to_string({activity_envelope, Skeleton})`. `sign/2` extracts key_id/algorithm/key-material from a KeySpec proplist, computes the v1 HMAC over canonical bytes, and appends the `:signature` pair. `cid_of/1` is a convenience accessor. Round-trip end-to-end through `envelope:verify_signature/2` verified (correct key passes, wrong key returns bad_signature). Step 6d split into 6d-cs (done) + 6d-publish (orchestration). `next/tests/outbox_construct.sh` 13/13. Erlang conformance 729/729.