mod: Ext 16 — ActivityPub-shaped decision export, 350/350

mod/decision->activity maps a decision to a moderation verb (remove→Delete,
ban→Block, hide/escalate→Flag, keep→no activity) shaped like an AP activity,
preserving the precise action. mod/decisions->activities batch-exports dropping
keeps. With wire (Ext 14) + fed trust (Phase 4) the federated moderation path is
end-to-end: decide → activity/wire → peer → trust-gate → apply. +17 tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plans/mod-on-sx.md

@@ -16,7 +16,7 @@ federation extension.
 
 ## Status (rolling)
 
-`bash lib/mod/conformance.sh` → **333/333** (roadmap + 15 extensions complete)
+`bash lib/mod/conformance.sh` → **350/350** (roadmap + 16 extensions complete)
 
 ## Ground rules
 
@@ -147,6 +147,12 @@ lib/mod/fed.sx
   derivation goal-by-goal with `[proved]`/`[unproved]` marks and unification
   bindings. E.g. `Report rc: escalate (rule: repeated-escalate)` … `[proved]
   report(rc, B, S), report_count(S, N), N >= 3  {B=ann, N=3, S=dave}`.
+- [x] **Ext 16 — ActivityPub-shaped export** (`lib/mod/activity.sx`, +17).
+  `mod/decision->activity` maps a decision to a moderation verb (remove→Delete,
+  ban→Block, hide/escalate→Flag, keep→no activity) shaped like an AP activity
+  ({:type :actor :object :summary}), the precise mod action preserved in :action.
+  `mod/decisions->activities` batch-exports, dropping keeps — ready for the
+  platform's AP event bus / federated peers.
 - [x] **Ext 15 — disjunctive conditions** (`policy.sx` + `tests/disjunction.sx`,
   +10). `(:any (list c1 c2 …))` compiles to Prolog disjunction `(g1 ; g2 ; …)`,
   completing the condition boolean algebra (AND via the :when list, `:not`, `:any`).
@@ -218,6 +224,11 @@ lib/mod/fed.sx
 
 ## Progress log
 
+- **Ext 16 — ActivityPub-shaped export, 350/350** (+17). Bridges mod-sx to the
+  wider rose-ash platform, which propagates cross-domain effects as AP-shaped
+  activities. Decisions become Flag/Delete/Block activities (keep = no-op); with
+  the wire format (Ext 14) and fed trust model (Phase 4) the federated moderation
+  path is now end-to-end: decide → activity/wire → peer → trust-gate → apply.
 - **Ext 15 — disjunctive conditions, 333/333** (+10). The condition DSL is now a
   full boolean algebra: AND (the :when list), `:not` (NAF), `:any` (Prolog `;`).
   cond->goal recurses, so the combinators nest arbitrarily — `:any` of `:not`s, an