fed-sx-m1: Step 6b-sig — pipeline:stage_signature/1,/2 (factory + direct) + 11 tests

plans/fed-sx-milestone-1.md

@@ -388,7 +388,7 @@ projection fold maintains it.)
 **Sub-deliverables:**
 - [x] **6a** — `pipeline:run_stages/2` driver — pure fold over a stage list of `(Activity) -> ok | {error, R}` funs, halts on first failure. `validate_inbound/1` + `validate_outbound/1` + `inbound_stages/0` + `outbound_stages/0` (empty lists for now). `next/tests/pipeline_driver.sh` (10 cases).
 - [x] **6b-env** — `pipeline:stage_envelope/1` delegating to `envelope:validate_shape/1`; wired into both `inbound_stages` and `outbound_stages`. `next/tests/pipeline_envelope.sh` (12 cases); pipeline_driver.sh updated to test the driver in isolation.
-- [ ] **6b-sig** — `pipeline:stage_signature/2` taking actor-state context, delegating to `envelope:verify_signature/2`. Needs a runtime-context shape since the driver only passes the activity.
+- [x] **6b-sig** — `pipeline:stage_signature/2` (direct call) + `stage_signature/1` (factory returning a context-bound stage fun). Not wired into default stage lists since ActorState isn't available at static-list build time; callers compose by `Stages = [..., pipeline:stage_signature(AS)]`. `next/tests/pipeline_signature.sh` (11 cases) covers direct + factory + composition + halt behaviour with stage_envelope.
 - [ ] **6c** — `stage_replay/1` (checks the log for existing activity id), `stage_activity_schema/1` (registry lookup + schema body eval is deferred — placeholder)
 - [ ] **6d** — `outbox:publish/2`: envelope construction, sign, validate_outbound, log:append, returns `{ok, #{cid, ap_id}}`
 - [ ] **6e** — HTTP handler for POST /activity glue (depends on Step 8 http server)
@@ -969,6 +969,7 @@ 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 6b-sig: `pipeline:stage_signature/2` direct call + `stage_signature/1` factory returning a context-bound stage fun closed over ActorState. Not wired into the default `inbound_stages`/`outbound_stages` lists because actor state isn't a static-build-time value; callers prepend the factory result to a stage list (`Stages = [stage_envelope, pipeline:stage_signature(AS)]`). `next/tests/pipeline_signature.sh` 11/11 covers direct + factory + composition with stage_envelope (including halt ordering: bad envelope halts before sig; good envelope + bad sig surfaces sig error). Erlang conformance 729/729.
 - **2026-05-28** — Step 6b-env: `pipeline:stage_envelope/1` wraps `envelope:validate_shape/1`; wired into both `inbound_stages` and `outbound_stages` lists. `validate_inbound`/`validate_outbound` now exercises the full envelope shape contract end-to-end (missing fields, signature sub-shape, non-list input). `next/tests/pipeline_envelope.sh` 12/12; `pipeline_driver.sh` refactored to test the driver against explicit stage lists rather than depending on the now-non-empty defaults. Split 6b in the plan into 6b-env (done) + 6b-sig (needs runtime context for actor-state). Erlang conformance 729/729.
 - **2026-05-28** — Step 6a: `next/kernel/pipeline.erl` — validation pipeline driver per design §14. `run_stages/2` is a pure fold over `(Activity) -> ok | {error, R}` funs, halting on first failure. Halt verified by inserting a post-error stage that would set a contradictory tag if it ran. `validate_inbound/1` + `validate_outbound/1` wrappers; concrete stage lists are empty (6b wires `stage_envelope`/`stage_signature`). Port quirk: `Pattern = Var` match-alias syntax unsupported — split into separate `Result = X, case Result of ...`. `next/tests/pipeline_driver.sh` 10/10. Step 6 broken into 6a–6e on the plan. Erlang conformance 729/729.
 - **2026-05-28** — Step 5b: `registry.erl` extended with gen_server callbacks + named-process API. `start_link/0` spawns the worker, registers it under the literal `registry` atom, returns the Pid (port returns raw Pid not `{ok, Pid}` — diverges from OTP). 3-arity `register`, 2-arity `lookup`, 1-arity `list` delegate to the pure /4 and /3 functions inside handle_call. Port note documented: `?MODULE` macro unsupported; tests must inline start_link with operations since spawned processes don't persist across separate `erlang-eval-ast` calls. `next/tests/registry_server.sh` 12/12. Erlang conformance 729/729.