fed-sx-m1: Step 8d-dispatch-post — format-aware POST /activity (cid_response_for + post_activity_response_for) + 13 tests

plans/fed-sx-milestone-1.md

@@ -520,7 +520,8 @@ publish(ActorId, ActivityRequest) ->
 - [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).
 - [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).
 - [x] **8d-content-type** — `content_type_for/1` maps format atoms to MIME-type binaries (text/plain, application/json, application/activity+json, application/sx, application/cbor). `ok_response/2(Body, Format)` builds a 200 response with the right Content-Type header. `next/tests/http_content_type.sh` (13 cases).
-- [ ] **8d-dispatch-rest** — Wire `ok_response/2` + format dispatch into `actor_doc_response`, `artifact_response`, `projection_response`, `cid_response`.
+- [x] **8d-dispatch-post** — POST `/activity` now threads the Accept format through both kernel-present (`cid_response_for/2` → `{"cid":"<cid>"}` for json / `(cid "<cid>")` for sx / raw bytes for cbor) and kernel-absent (`post_activity_response_for/1` → `{"status":"stub"}` / `(status "stub")` / etc.) paths. `next/tests/http_post_format.sh` (13 cases) covers shape + Content-Type for both stub and publish paths.
+- [ ] **8d-dispatch-get** — Same treatment for `actor_doc_response`, `artifact_response`, `projection_response` on the GET paths.
 
 **Deliverables:**
 
@@ -999,6 +1000,7 @@ 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-post: `handle_post_activity` extracts the Accept format via `accept_format_from/1` and threads it into `publish_if_kernel/2`. Both success paths emit format-specific bodies: `cid_response_for/2` produces `{"cid":"<cid>"}\n` (json/activity_json), `(cid "<cid>")\n` (sx), raw CID bytes (cbor), or the existing text form; `post_activity_response_for/1` mirrors for the kernel-absent stub. Each response carries the matching Content-Type. End-to-end POSTs with `Accept: application/json` / `application/sx` verified through the full HTTP→nx_kernel→publish→cid_response_for chain. `next/tests/http_post_format.sh` 13/13. Erlang conformance 729/729.
 - **2026-05-28** — Step 8d-content-type: `content_type_for/1` maps format atoms to MIME-type binaries — text/plain (10b), application/json (16b), application/activity+json (25b), application/sx (14b), application/cbor (16b); unknown formats fall through to text/plain. `ok_response/2(Body, Format)` constructs a 200 response with `{headers, [{<<"content-type">>, MIME}]}`. Lowercase header key matches how the BIF wrapper normalises request headers. `ok_response/1` still produces the empty-headers shape — backward compat preserved. `next/tests/http_content_type.sh` 13/13. Erlang conformance 729/729.
 - **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.