fed-sx-m1: Step 8d-dispatch-cap — capabilities_body_for + Accept-aware route + 13 tests

plans/fed-sx-milestone-1.md

@@ -518,7 +518,8 @@ publish(ActorId, ActivityRequest) ->
 - [x] **8c-post-publish-srv** — gen_server wrapper around nx_kernel: `start_link/3`, named-process `publish/1`, `query/0`, `log_tip/0`, `with_projections/1`, `stop/0`. `next/tests/nx_kernel_server.sh` (11 cases). HTTP layer integration follows.
 - [x] **8c-post-publish-http** — POST `/activity` handler now calls `nx_kernel:publish/1` when the kernel process is registered; falls back to the existing stub when not. Success → 200 with `cid: <cid>\n` body via `cid_response/1`; sig/replay failures → 422 via `validation_failed_response/0`. `next/tests/http_publish.sh` (10 cases).
 - [x] **8d-accept** — `accept_format/1` + `accept_format_from/1` parse the Accept header into `:activity_json | :json | :sx | :cbor | :text`. Priority: activity+json > json > sx > cbor; everything else falls to text. `next/tests/http_accept.sh` (13 cases).
-- [ ] **8d-dispatch** — Wire format dispatch into responses (e.g., the `cid_response`/`actor_doc_response`/etc. emit body shapes matching the chosen format).
+- [x] **8d-dispatch-cap** — `capabilities_body_for/1` returns distinct stubs per format (json `{...}`, sx `(...)`, cbor `A1 64 caps 69 fed-sx-m1`); activity_json shares the json body. Route intercepts GET capabilities to thread the Accept format through `accept_format_from/1`. `next/tests/http_capabilities_format.sh` (13 cases).
+- [ ] **8d-dispatch-rest** — Same treatment for `actor_doc_response`, `artifact_response`, `projection_response`, `cid_response` (plus Content-Type headers).
 
 **Deliverables:**
 
@@ -997,6 +998,7 @@ 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 8d-dispatch-cap: `capabilities_body_for/1` returns distinct byte sequences per format — text reuses the existing `capabilities_body/0`; json/activity_json share `{"caps":"fed-sx-m1"}`; sx returns `(caps "fed-sx-m1")`; cbor returns a minimal `A1 64 caps 69 fed-sx-m1` map. Route now intercepts GET `/.well-known/sx-capabilities` to pull the Accept format via `accept_format_from/1` and dispatch through `capabilities_body_for`. Unknown formats fall back to text. POST capabilities still 404 (only GET handled). `next/tests/http_capabilities_format.sh` 13/13 verifies all formats + the intercept + no-Accept default. Content-Type headers not yet set (8d-dispatch-rest covers headers + applying the same shape to actor/artifact/projection/cid responses). Erlang conformance 729/729.
 - **2026-05-28** — Step 8d-accept: `accept_format/1` + `accept_format_from/1` parse the Accept header into a content-negotiation atom. Priority order via successive `match_prefix` checks: application/activity+json → `activity_json`; application/json → `json`; application/sx → `sx`; application/cbor → `cbor`; everything else (including nil / empty / non-binary) → `text`. Comma-separated lists with activity+json first still resolve to activity_json — leading-prefix match is sufficient for v1 envelopes. Step 8d split into 8d-accept (done) + 8d-dispatch (wire into response bodies). `next/tests/http_accept.sh` 13/13. Erlang conformance 729/729.
 - **2026-05-28** — Step 5c-populate: `bootstrap:populate_registry/0` walks `read_genesis` output and calls `registry:register/3` (gen_server API) for each entry. Total return is 31 = 3 + 10 + 7 + 3 + 3 + 2 + 3 across the seven kinds, matching the manifest authored in Step 4. `next/tests/bootstrap_populate.sh` 14/14 verifies per-kind counts + lookups against known names (`activity_types/create`, `object_types/define-activity`, `validators/envelope-shape`). Erlang conformance 729/729.
 - **2026-05-28** — Step 9-pre-fold: in-process integration test proving the full POST → publish → broadcast → projection-fold chain. With `projection:start_link` + `nx_kernel:start_link` + `nx_kernel:with_projections([p_count, p_collect])`, three authorized POST `/activity` calls advance both projections to 3 — and the kernel's log to 3 entries — and the projection's collected activity carries the POST body as `:object`. Unauthorized or sig-failed POSTs leave projection state unchanged. Step 9a/b proper (curl-driven smoke tests) wait on Step 8b-start (TCP) + Define\* SX-source eval bridge, but the structural chain is already verified end-to-end. `next/tests/http_publish_fold.sh` 10/10. Erlang conformance 729/729. Step 9 split into 9-pre-fold (done) + 9a + 9b.