chore(engine): server hygiene batch — workers tests, surname dedup, save pin (T-1063, T-1064)

- workers/pool.rs: 5 new tests; catch_unwind keeps worker threads alive on
  handler panic (in-flight request loss unchanged, pinned by test + #843
  docs); stubs.rs no longer falsely claims the pool is tested
- save/load: execute_save_load pinned .after(Storyteller) so the scheduler
  cannot legally save pre-Input state; exclusive-system exception recorded
  in tick_phases.rs rules
- surname corpus extracted to bin/shared/surname_corpus.rs (both economy
  generators import it; byte-identical output verified on 23.6MB+1.45MB
  TOMLs); all three stamp/watch registries updated
- generator_spike gated behind non-default 'generator-spike' feature
- economy.rs: 11 new D-181 signal-derivation tests on the new
  econ_sim Simulation::from_economy in-memory constructor
- perception exemption comments now state the consumer sort contract;
  unused bytemuck removed; rayon comment corrected; the 22 allow(dead_code)
  documented as serde schema enforcement

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tooling/econ-sim/src/sim.rs

@@ -54,13 +54,23 @@ impl Simulation {
 
         let conn = db::open_db(&db_pathbuf);
         let economy = db::load_economy(&conn);
+        Ok(Self::from_economy(economy, run_seed))
+    }
+
+    /// Build a simulation directly from an in-memory [`db::Economy`] — no DB file.
+    ///
+    /// Identical initialization to [`Simulation::load`] after the DB read:
+    /// deterministic productivity/shadow seeding from `run_seed`, warm-start
+    /// node states. Intended for unit tests and embedded callers that
+    /// construct small, fully-controlled economies (T-1064).
+    pub fn from_economy(economy: db::Economy, run_seed: u64) -> Self {
         let productivity = seed::seed_all_productivity(&economy, run_seed);
         let shadow = currency::seed_shadow_economy(&economy, run_seed);
         let adjacency = trade::build_adjacency(&economy);
         let archetypes = agents::build_archetype_map(economy.corp_archetype_data.clone());
         let nodes = model::init_nodes(&economy);
 
-        Ok(Simulation {
+        Simulation {
             economy,
             productivity,
             shadow,
@@ -72,7 +82,7 @@ impl Simulation {
             tick: 0,
             alpha: model::ALPHA,
             beta: trade::BETA,
-        })
+        }
     }
 
     /// Try to load from the auto-detected DB path (same search as the CLI binary).