feat(v1.1.2-docs): Rhai docs:: SDK module + ctx.event.docs + bridge tests

The docs:: SDK bridge mirrors kv::'s collection-handle pattern: a
custom Rhai type DocsHandle captures (collection, service, cx) once
via docs::collection(name), and methods bind via engine.register_fn
so scripts use dot-notation (users.create(...), users.find(...),
etc.). app_id never appears in the script-visible call shape — the
service derives it from cx.app_id, preserving cross-app isolation.

Methods registered: create, get, find, find_one, update, delete,
list (zero-arg and one-arg map-shaped overloads). The find filter
goes through dynamic_to_json -> DocsService::find -> docs_filter
parser; unsupported operators surface to Rhai with the parser's
verbatim error message (including the v1.2 pointer).

The doc envelope per Decision D:
  #{ id: "uuid", data: #{...user data...},
     created_at: "ISO-8601", updated_at: "ISO-8601" }

engine.rs trigger_event_to_dynamic gains a Docs arm that builds
ctx.event.docs = #{ collection, id, data, prev_data } where data
and prev_data follow the variant's Option<Value> -> () | map shape.

15 bridge integration tests under tests/sdk_docs.rs exercise the
round-trip via tokio::task::spawn_blocking. Covers create/get/find/
find_one/update/delete/list semantics, $in + $gt operators, the
unsupported-operator throw with v1.2 pointer, invalid-UUID rejection
on get/update/delete, the doc envelope's shape (id is string, data
is map, timestamps are strings), and the load-bearing cross-app
isolation guarantee. sdk_kv.rs is updated to take the new docs
field on Services::new.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/executor-core/src/engine.rs

@@ -278,6 +278,27 @@ fn trigger_event_to_dynamic(event: &TriggerEvent) -> Dynamic {
             );
             m.insert("kv".into(), kv_map.into());
         }
+        TriggerEvent::Docs {
+            op,
+            collection,
+            id,
+            data,
+            prev_data,
+        } => {
+            m.insert("op".into(), op.as_str().into());
+            let mut docs_map = Map::new();
+            docs_map.insert("collection".into(), collection.clone().into());
+            docs_map.insert("id".into(), id.clone().into());
+            docs_map.insert(
+                "data".into(),
+                data.clone().map_or(Dynamic::UNIT, json_to_dynamic),
+            );
+            docs_map.insert(
+                "prev_data".into(),
+                prev_data.clone().map_or(Dynamic::UNIT, json_to_dynamic),
+            );
+            m.insert("docs".into(), docs_map.into());
+        }
         TriggerEvent::DeadLetter {
             dead_letter_id,
             original,