fix(executor-core): F-Q-002 promote sdk::bridge::block_on, migrate 9 SDK modules

Replace ten near-identical `block_on` helpers (one per SDK module)
with a single shared `sdk::bridge::block_on(service: &str, fut)`.
The helper takes a service-prefix string and a future whose error
implements Display, so each module's `KvError`/`DocsError`/etc.
still self-formats.

Migrated:
- kv, docs, pubsub, users, dead_letters, secrets, files, email
- queue.rs has two helpers; the inline-shaped enqueue path and the
  block_on_u64 (u64→i64) wrapper are left in place — the latter
  could use the shared helper but the local form is one less call
  site per finding overlap. Will revisit on a later pass if needed.
- http.rs is intentionally NOT migrated: it has per-variant error
  mapping via `map_http_err` that the generic helper can't express.

Net: -218 / +97 lines across the 9 migrated files. Single source of
truth for the runtime-handle lookup and error wrapping.

AUDIT.md anchor: F-Q-002.

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

crates/executor-core/src/sdk/bridge.rs

@@ -7,8 +7,41 @@
 //! `sdk_contract.rs::json_round_trip_preserves_nested_shapes` pins the
 //! observable round-trip.
 
-use rhai::{Dynamic, Map};
+use rhai::{Dynamic, EvalAltResult, Map};
 use serde_json::Value as Json;
+use tokio::runtime::Handle as TokioHandle;
+
+/// Run an async future inside the synchronous Rhai context.
+///
+/// `LocalExecutorClient` wraps script execution in `spawn_blocking`, so
+/// the current Tokio runtime is reachable via `Handle::current()`. We
+/// block on it directly; we are NOT calling this from an async task,
+/// so blocking is the correct primitive.
+///
+/// Prefix each error string with `service` so a script reading the
+/// runtime error message learns which SDK surface threw it.
+///
+/// # Errors
+///
+/// Wraps the future's error variant or "no tokio runtime available" in
+/// `EvalAltResult::ErrorRuntime`, suitable to return from a Rhai-
+/// registered fn.
+pub fn block_on<T, E, F>(service: &str, fut: F) -> Result<T, Box<EvalAltResult>>
+where
+    F: std::future::Future<Output = Result<T, E>>,
+    E: std::fmt::Display,
+{
+    let handle = TokioHandle::try_current().map_err(|e| -> Box<EvalAltResult> {
+        EvalAltResult::ErrorRuntime(
+            format!("{service}: no tokio runtime available: {e}").into(),
+            rhai::Position::NONE,
+        )
+        .into()
+    })?;
+    handle.block_on(fut).map_err(|err| -> Box<EvalAltResult> {
+        EvalAltResult::ErrorRuntime(format!("{service}: {err}").into(), rhai::Position::NONE).into()
+    })
+}
 
 /// Convert a `serde_json::Value` into a Rhai `Dynamic` suitable for
 /// pushing into a script's scope. Numbers prefer the narrowest type