fed-sx-m2: Step 4d — outbox listing from log + pagination + 8 tests

Per-actor GET /actors/<id>/outbox now reads the bucket's log via
new nx_kernel:log_state_for/1 gen_server export and renders the
paged CID list.

nx_kernel additions:
  log_state_for/1 gen_server call returning {ok, LogState} for
  the named actor (mirrors log_tip_for/1's shape).

http_server additions:
  - with_request_query/2 bakes Req's :query binary into Cfg as
    {request_query, Q} so sub-resource handlers can parse params
    without taking the Req as another arg
  - kernel_actor_log_data/2 -> {Tip, Entries} via
    nx_kernel:log_tip_for + log_state_for + log:entries
  - parse_page/1 reads ?page=N (default 1, non-digits -> 1)
  - page_size/0 returns 5 (test-friendly; production picks 20+)
  - page_slice/2 + drop_take/3 + take/2 for the page extraction
  - entry_cids/1 maps entries to :id CID binaries via envelope
  - actor_outbox_full_response_for/5 renders text / JSON / SX:
      text:  outbox: <id>\ntip: N\npage: P\nitem: <cid>\n...
      json:  {"outbox":"<id>","tip":N,"page":P,"items":[...]}
      sx:    (outbox "<id>" :tip N :page P :items (...))
    Empty page degrades to actor_outbox_with_tip_response_for so
    epochs 50-57 from Step 4c still pass — the prefix is preserved.

8 new cases in next/tests/http_multi_actor.sh (41/41 total):
  - 1 publish -> body contains outbox/tip=1/page=1/item: prefix
  - 3 publishes -> body contains tip=3/page=1/item: prefix
  - page=2 with 3 items -> empty page degrades to tip-only body
  - 6 publishes page=1 -> tip=6/page=1/item: prefix
  - 6 publishes page=2 -> tip=6/page=2/item: prefix
  - JSON body shape with items array (1 entry)
  - SX body shape with :items list (1 entry)
  - bad ?page=bad falls back to page 1

Conformance 761/761. 117/117 across 11 Step-4-adjacent suites
(http_multi_actor, http_route, http_publish, http_post_format,
http_marshal, http_publish_fold, http_listen_bif, http_server_start,
nx_kernel_multi, nx_kernel_server, bootstrap_start, actor_lifecycle).

Substrate gotcha logged: named recursive funs fun F(...) -> F(...)
end aren't supported by the parser ('fun-ref syntax not yet
supported'); binary:matches/2 and lists:foreach/2 aren't registered.
Tests prove behaviour via match_prefix substring checks rather than
counting occurrences.

plans/fed-sx-milestone-2.md

@@ -300,10 +300,19 @@ token; the token now maps to an `:actor_id` rather than a fixed `alice`.
   delivery); the live handler does a bare `nx_kernel:log_tip_for/1`
   + integer guard instead. 8 new cases in `http_multi_actor.sh`
   (33/33 total).
-- [ ] **4d** — Per-actor outbox listing reads from the named
-  bucket's log entries via `nx_kernel:actor_log_state/2`, content-
-  negotiates as today (text / json / sx). `?page=N` pagination
-  layered on top using `log:replay/3`.
+- [x] **4d** — Per-actor outbox listing reads from the named
+  bucket's log entries via new `nx_kernel:log_state_for/1`
+  gen_server export. `actor_outbox_full_response_for/5` renders
+  text / JSON / SX bodies with `:tip`, `:page`, and the page's
+  `:items` CID list. Empty pages degrade to the 4c tip-only body
+  to preserve back-compat with epochs 50-57. `?page=N` pagination
+  parsed at `route/2` time and threaded via Cfg as
+  `{request_query, Q}`; `page_size/0` returns 5 (proof of concept
+  — production picks 20+). 8 new cases in `http_multi_actor.sh`
+  (41/41 total). Substrate gotcha: named recursive funs
+  `fun F(...) -> ... F(...) end` not supported; `binary:matches/2`
+  and `lists:foreach/2` not registered — tests prove behaviour
+  via `match_prefix` substring checks rather than counting.
 - [ ] **4e** — POST /actors/<id>/inbox stays a 202 stub for 4a-4d.
   Step 5 lands the real ingestion pipeline (sig verify + inbox-
   bucket append + projection broadcast).
@@ -749,6 +758,23 @@ proceed.
 
 Newest first.
 
+- **2026-06-06** — Step 4d: per-actor outbox listing + pagination.
+  New `nx_kernel:log_state_for/1` gen_server export returns
+  `{ok, LogState}` for an actor. `actor_outbox_response_for/3`
+  now extracts `{Tip, Entries}` via `kernel_actor_log_data/2`,
+  parses `?page=N` from the Req's `:query` field (threaded
+  through Cfg as `{request_query, Q}`), and renders a paged
+  body. Text body adds `page: N\nitem: <cid>\n...`; JSON adds
+  `"page":N,"items":[...]`; SX adds `:page N :items (...)`.
+  Empty pages (out-of-range or actor-with-no-publishes) degrade
+  back to the 4c tip-only shape, preserving epochs 50-57.
+  `page_size/0` is 5 for tests (production picks 20+). 8 new
+  cases in `http_multi_actor.sh` (41/41 total). Conformance
+  761/761. 117/117 across 11 Step-4-adjacent suites. **Gotcha**
+  noted: named recursive funs `fun F(...) -> ... F(...) end`
+  fail with "fun-ref syntax not yet supported"; `binary:matches/2`
+  and `lists:foreach/2` aren't registered in this substrate.
+
 - **2026-06-06** — Step 4c: route/3 with kernel access.
   `http_server:route/3(Req, Cfg, Kernel)` folds the kernel
   reference into Cfg as `{kernel, _}`. Dispatch chain refactored