refactor: implement base/modifier separation for variable reactivity

Introduce a distinction between base values (set via `/set` or
declarations) and active modifiers (applied via tags). This ensures
tag transitions and numeric modifiers are calculated correctly during
cascades.

- Refactor `VariableView` to use a flat list with hover popups for
  declarations and active modifiers.
- Update `command-dispatcher` to use `getCombined` for accurate
  value lookups and `setBase` for variable updates.
- Update `var-reactivity` to manage `baseValues`, `activeMods`, and
  `sourceActivations` separately.
- Export new utility functions for accessing combined values,
  modifiers, and declaration expressions.

src/components/journal/command-dispatcher.ts

@@ -11,7 +11,7 @@ import { parseInput } from "./command-parser";
 import { resolveRollPayload } from "./types/roll";
 import { resolveSparkPayload } from "./types/spark";
 import { evaluateExpression, expressionIsTag } from "./variable-expression";
-import { computeCascade } from "./var-reactivity";
+import { computeCascade, getCombined, setBase } from "./var-reactivity";
 import type { VarDeclaration, TagModifier } from "./declare-parser";
 
 // ---------------------------------------------------------------------------
@@ -140,7 +140,9 @@ function dispatchSet(
   }
 
   const key = p.key;
-  const oldValue = ctx.variables[key] ?? undefined;
+  // Use getCombined for old value so tag transitions are detected correctly
+  // even when the variable has active mods.
+  const oldValue = getCombined(key);
   let newValue: string;
 
   try {
@@ -152,11 +154,12 @@ function dispatchSet(
       // Bare tag value
       newValue = p.expr.trim();
     } else if (p.expr) {
-      // Numeric expression — evaluate
+      // Numeric expression — evaluate using combined values
       const result = evaluateExpression(p.expr, {
         lookup: (name: string) => {
           const k = "$" + name;
-          return ctx.variables[k] ?? undefined;
+          // Use getCombined for accurate values including active mods
+          return k === key ? undefined : getCombined(k);
         },
       });
       newValue = String(result.value);
@@ -170,12 +173,11 @@ function dispatchSet(
     };
   }
 
-  // Send the direct set
-  const r1 = sendMessage("var", { action: "set", key, value: newValue });
-  const u1 = unwrap(r1);
-  if (!u1.ok) return u1;
+  // Update base value so getCombined returns the correct new value
+  // during cascade computation
+  setBase(key, newValue);
 
-  // Build working variable store for cascade
+  // Build working variable store for cascade (includes the new value)
   const workingVars = { ...ctx.variables, [key]: newValue };
 
   // Compute cascade (tag activation/deactivation + declaration re-eval)
@@ -189,6 +191,14 @@ function dispatchSet(
     console.warn("[dispatch] cascade error:", e);
   }
 
+  // Send the direct set last so cascade messages arrive first.
+  // Use getCombined so the stream store receives the correct value
+  // (base + active mods) rather than just the raw base.
+  const combinedValue = getCombined(key);
+  const r1 = sendMessage("var", { action: "set", key, value: combinedValue });
+  const u1 = unwrap(r1);
+  if (!u1.ok) return u1;
+
   return { ok: true };
 }