fix(journal): re-init reactivity and drop var del

Make the reactivity engine re-initialize when the loaded declarations
change instead of only at import. ensureReactivity() reads the live
completions signal, compares a signature, and rebuilds from the store
(with exact bases) only when needed; dispatchCommand calls it before each
dispatch. Remove the unused DispatchContext.declarations/tagModifiers
fields, which were mount-time snapshots and could not be trusted.

Build initReactivity's maps into locals and commit only after the
circular check passes, so a failed re-init leaves the previous engine
intact; clear inFlight on commit.

Drop the unreachable var "del" action from the schema, render, and
reducer.

src/components/journal/command-dispatcher.ts

@@ -12,7 +12,7 @@ import { resolveRollPayload } from "./types/roll";
 import { resolveSparkPayload } from "./types/spark";
 import { evaluateExpression, exprValueToString } from "./variable-expression";
 import { computeCascade, getCombined, setBase } from "./var-reactivity";
-import type { VarDeclaration, TagModifier } from "./declare-parser";
+import { ensureReactivity } from "./completions";
 
 // Tagmap pattern: "#warrior:1;#druid:2". Also accepts bare "#tag" as shorthand.
 const BARE_TAG_PATTERN = /^#[a-zA-Z_][a-zA-Z0-9_]*$/;
@@ -58,10 +58,6 @@ export interface DispatchContext {
   }[];
   /** Current runtime variable values */
   variables: Record<string, string>;
-  /** Variable declarations (from role=declare blocks) */
-  declarations: VarDeclaration[];
-  /** Tag modifiers (from role=declare blocks) */
-  tagModifiers: TagModifier[];
 }
 
 /**
@@ -74,6 +70,10 @@ export async function dispatchCommand(
   const raw = ctx.command.trim();
   if (!raw) return { ok: false, error: "Empty command" };
 
+  // Make sure the engine reflects the currently loaded declarations; this
+  // re-initializes only when they changed since the last dispatch.
+  ensureReactivity();
+
   // Observers can only send chat
   if (ctx.role === "observer") {
     const result = sendMessage("chat", { text: raw });