refactor(token_optimizer): Phase B language-advantage pass — dichotomy wave

Op::run — the enum owns its execution: every variant's semantics live
next to its name and the exhaustive match moved into the type (adding an
op without semantics stays a compile error, now enforced where the
behavior lives, not at the call site). _write_snapshot_doc as a
filter_map-collect iterator chain over the transfer array (no mutable
accumulator; the entry-key projection is one declarative pipeline).

Behavior unchanged: battery 7/7, live parity 60/60, clippy -D warnings
clean, module tests 5/5 both pins. Evidence: verification/to-phaseb-parity.exit.

src/rust/token_optimizer/src/lib.rs

@@ -307,12 +307,13 @@ fn snapshot_doc(st: &State) -> Value {
 /// JSON object keyed by entry key). The makedirs/tmp-file/`os.replace`
 /// write stays facade (I/O law).
 fn _write_snapshot_doc(snap: &Value) -> Value {
-    let mut cache = Map::new();
-    for e in snap.get("cache").and_then(Value::as_array).into_iter().flatten() {
-        if let Some(k) = e.get("key").and_then(Value::as_str) {
-            cache.insert(k.to_string(), e.clone());
-        }
-    }
+    let cache: Map<String, Value> = snap
+        .get("cache")
+        .and_then(Value::as_array)
+        .into_iter()
+        .flatten()
+        .filter_map(|e| Some((e.get("key")?.as_str()?.to_string(), e.clone())))
+        .collect();
     json!({"cache": cache, "stats": snap.get("stats").cloned().unwrap_or(Value::Null)})
 }
 
@@ -505,6 +506,37 @@ impl Op {
             other => Err(format!("unknown op: {other}")),
         }
     }
+
+    /// Phase B: the enum owns its execution — every variant's behavior
+    /// lives next to its name and the match stays exhaustive (adding an op
+    /// without semantics is a compile error, not a silent fallthrough).
+    fn run(
+        self,
+        st: &mut State,
+        args: &Value,
+        now_iso: &str,
+        now: f64,
+        snap: &mut Option<Value>,
+    ) -> Result<Value, String> {
+        let a = Args::from_value(args);
+        Ok(match self {
+            Op::GetOptimizer => {
+                let text = args.get("storage_text").and_then(Value::as_str);
+                *st = get_optimizer(text);
+                st._to_state()
+            }
+            Op::GetStaticCache => Value::String(get_static_cache(st, a.persona, now_iso, now, snap)),
+            Op::GetDynamicCache => Value::String(get_dynamic_cache(st, a.context, now_iso, now, snap)),
+            Op::OptimizePrompt => optimize_prompt(st, a.text, a.context, a.persona, now_iso, now, snap),
+            Op::GetStatus => get_status(st),
+            Op::GetCacheStats => get_cache_stats(st),
+            Op::MarkDirty => {
+                mark_dirty(st);
+                Value::Null
+            }
+            Op::SaveIfDirty => json!({"save": maybe_save(st, now, snap)}),
+        })
+    }
 }
 
 /// One borrowed argument view over the wire doc (Phase B: zero-copy —
@@ -538,25 +570,7 @@ fn _run_kernel(
     now: f64,
     snap: &mut Option<Value>,
 ) -> Result<Value, String> {
-    let op = Op::parse(op)?;
-    let a = Args::from_value(args);
-    Ok(match op {
-        Op::GetOptimizer => {
-            let text = args.get("storage_text").and_then(Value::as_str);
-            *st = get_optimizer(text);
-            st._to_state()
-        }
-        Op::GetStaticCache => Value::String(get_static_cache(st, a.persona, now_iso, now, snap)),
-        Op::GetDynamicCache => Value::String(get_dynamic_cache(st, a.context, now_iso, now, snap)),
-        Op::OptimizePrompt => optimize_prompt(st, a.text, a.context, a.persona, now_iso, now, snap),
-        Op::GetStatus => get_status(st),
-        Op::GetCacheStats => get_cache_stats(st),
-        Op::MarkDirty => {
-            mark_dirty(st);
-            Value::Null
-        }
-        Op::SaveIfDirty => json!({"save": maybe_save(st, now, snap)}),
-    })
+    Op::parse(op)?.run(st, args, now_iso, now, snap)
 }
 
 // ── FFI (doc-envelope law) ──────────────────────────────────────────────

verification/to-phaseb-parity.exit

@@ -0,0 +1 @@
+0