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.

next/kernel/nx_kernel.erl

@@ -17,7 +17,7 @@
 %% gen_server API
 -export([start_link/3, publish/1, query/0, log_tip/0,
          with_projections/1, stop/0,
-         add_actor/3, publish_to/2, log_tip_for/1,
+         add_actor/3, publish_to/2, log_tip_for/1, log_state_for/1,
          actors/0, state_for/1, bucket_for/1,
          with_projections_for/2,
          bootstrap_actor/3]).
@@ -321,6 +321,9 @@ publish_to(ActorId, Request) ->
 log_tip_for(ActorId) ->
     gen_server:call(nx_kernel, {log_tip_for, ActorId}).
 
+log_state_for(ActorId) ->
+    gen_server:call(nx_kernel, {log_state_for, ActorId}).
+
 actors() ->
     gen_server:call(nx_kernel, get_actors).
 
@@ -366,6 +369,8 @@ handle_call({publish_to, ActorId, Request}, _From, State) ->
     end;
 handle_call({log_tip_for, ActorId}, _From, State) ->
     {reply, actor_log_tip(ActorId, State), State};
+handle_call({log_state_for, ActorId}, _From, State) ->
+    {reply, actor_log_state(ActorId, State), State};
 handle_call(get_actors, _From, State) ->
     {reply, actors(State), State};
 handle_call({state_for, ActorId}, _From, State) ->