fix(journal): surface variable eval errors

Collect and report failed declarations, failed tag modifier expressions, and
circular dependencies instead of swallowing them. Diagnostics are deduped,
logged with key/expression context, cleared on re-init, and exposed through
useJournalCompletions and the VariableView warning banner. A bad declaration
no longer aborts the rest of a cascade.

Reject malformed numeric literals in the tokenizer so inputs like "1.2.3"
throw instead of being truncated by parseFloat.

src/cli/completions/variable-system.test.ts

@@ -40,6 +40,7 @@ import {
   getDeclExpr,
   extractDependencies,
   rebuildReactivityFromStore,
+  getReactivityDiagnostics,
 } from "../../components/journal/var-reactivity";
 import { parseInput } from "../../components/journal/command-parser";
 import {
@@ -396,6 +397,15 @@ describe("evaluateExpression", () => {
     ).toThrow("Unexpected end");
   });
 
+  test("throws on malformed number literals", () => {
+    expect(() =>
+      evaluateExpression("1.2.3", { lookup: () => undefined }),
+    ).toThrow("Invalid number literal");
+    expect(() =>
+      evaluateExpression("1.", { lookup: () => undefined }),
+    ).toThrow("Invalid number literal");
+  });
+
   test("handles decimal numbers", () => {
     const result = evaluateExpression("3.5 + 2.5", { lookup: () => undefined });
     expect(result.value).toEqual({ kind: "number", value: 6 });
@@ -574,6 +584,113 @@ describe("var-reactivity", () => {
     });
   });
 
+  describe("diagnostics", () => {
+    test("reports a declaration that fails to evaluate", () => {
+      const warn = jest.spyOn(console, "warn").mockImplementation(() => {});
+      initReactivity({
+        declarations: [
+          { key: "$hp", expression: "10 + 5" },
+          { key: "$bad", expression: "#warrior * 2" },
+        ],
+        tagModifiers: [],
+      });
+
+      const results = computeInitialValues(store());
+      expect(results.find((r) => r.key === "$hp")?.value).toBe("15");
+      expect(results.find((r) => r.key === "$bad")).toBeUndefined();
+
+      const diags = getReactivityDiagnostics();
+      expect(diags).toHaveLength(1);
+      expect(diags[0].kind).toBe("declaration");
+      expect(diags[0].key).toBe("$bad");
+      expect(diags[0].expression).toBe("#warrior * 2");
+      warn.mockRestore();
+    });
+
+    test("dedupes repeated failures of the same expression", () => {
+      const warn = jest.spyOn(console, "warn").mockImplementation(() => {});
+      initReactivity({
+        declarations: [{ key: "$bad", expression: "#warrior * 2" }],
+        tagModifiers: [],
+      });
+
+      computeInitialValues(store());
+      computeInitialValues(store());
+      expect(getReactivityDiagnostics()).toHaveLength(1);
+      warn.mockRestore();
+    });
+
+    test("clears diagnostics on re-init", () => {
+      const warn = jest.spyOn(console, "warn").mockImplementation(() => {});
+      initReactivity({
+        declarations: [{ key: "$bad", expression: "#warrior * 2" }],
+        tagModifiers: [],
+      });
+      computeInitialValues(store());
+      expect(getReactivityDiagnostics()).toHaveLength(1);
+
+      initReactivity({ declarations: [], tagModifiers: [] });
+      expect(getReactivityDiagnostics()).toHaveLength(0);
+      warn.mockRestore();
+    });
+
+    test("records a diagnostic when declarations are circular", () => {
+      const warn = jest.spyOn(console, "warn").mockImplementation(() => {});
+      expect(() =>
+        initReactivity({
+          declarations: [
+            { key: "$a", expression: "$b + 1" },
+            { key: "$b", expression: "$a + 1" },
+          ],
+          tagModifiers: [],
+        }),
+      ).toThrow();
+
+      const diags = getReactivityDiagnostics();
+      expect(diags).toHaveLength(1);
+      expect(diags[0].kind).toBe("init");
+      warn.mockRestore();
+    });
+
+    test("reports a tag modifier that fails to evaluate", () => {
+      const warn = jest.spyOn(console, "warn").mockImplementation(() => {});
+      initReactivity({
+        declarations: [],
+        tagModifiers: [
+          { tag: "#warrior", target: "$hp", expression: "#x * 2", threshold: 1 },
+        ],
+      });
+
+      setBase("$class", "#warrior:1");
+      computeCascade("$class", undefined, store({ $class: "#warrior:1" }));
+
+      const diags = getReactivityDiagnostics();
+      expect(diags).toHaveLength(1);
+      expect(diags[0].kind).toBe("modifier");
+      expect(diags[0].key).toBe("$hp");
+      expect(diags[0].tag).toBe("#warrior");
+      expect(diags[0].source).toBe("$class");
+      warn.mockRestore();
+    });
+
+    test("keeps cascading other dependents when a declaration fails", () => {
+      const warn = jest.spyOn(console, "warn").mockImplementation(() => {});
+      initReactivity({
+        declarations: [
+          { key: "$bad", expression: "$con * #warrior" },
+          { key: "$good", expression: "$con + 1" },
+        ],
+        tagModifiers: [],
+      });
+
+      const cascade = computeCascade("$con", undefined, store({ $con: "5" }));
+      expect(cascade.find((r) => r.key === "$good")?.value).toBe("6");
+      expect(cascade.find((r) => r.key === "$bad")).toBeUndefined();
+      expect(getReactivityDiagnostics().some((d) => d.key === "$bad")).toBe(true);
+      warn.mockRestore();
+    });
+  });
+
   describe("getCombined / setBase", () => {
     test("returns base value when no mods", () => {
       initReactivity({ declarations: [], tagModifiers: [] });