test: add coverage for ListSources (Go) and cssVar (canvas)

Go — workspace-server/internal/handlers/plugins_sources_test.go:
  - TestListSources_ReturnsSchemes: verifies the handler returns a 200
    with a schemes array from the real plugin registry (local + github).

Canvas — canvas/src/lib/__tests__/theme.test.ts:
  - Tests cssVar() for all 23 ColorToken variants (warm-paper surface
    tokens + always-dark tokens).
  - Verifies hyphenated tokens are handled correctly.
  - Confirms output is a plain string usable as an inline style prop value.
  - Guards against regressions as the ColorToken union is extended.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

canvas/src/lib/__tests__/theme.test.ts

@@ -0,0 +1,66 @@
+// @vitest-environment jsdom
+/**
+ * Tests for theme.ts — cssVar() function and ColorToken type.
+ *
+ * cssVar is intentionally simple (string concatenation) — these tests guard
+ * against regressions as ColorToken is extended and against typos in the
+ * token-name → CSS variable mapping.
+ */
+import { describe, it, expect } from "vitest";
+import { cssVar, type ColorToken } from "../theme";
+
+describe("cssVar", () => {
+  it("wraps each known token in a var() reference", () => {
+    const tokens: ColorToken[] = [
+      "surface",
+      "surface-elevated",
+      "surface-sunken",
+      "surface-card",
+      "line",
+      "line-soft",
+      "ink",
+      "ink-mid",
+      "ink-soft",
+      "accent",
+      "accent-strong",
+      "warm",
+      "good",
+      "bad",
+      "bg",
+      "bg-elev",
+      "bg-card",
+      "line-strong",
+      "ink-mute",
+      "ink-dim",
+      "accent-dim",
+      "plasma",
+      "warn",
+    ];
+    for (const token of tokens) {
+      expect(cssVar(token)).toBe(`var(--color-${token})`);
+    }
+  });
+
+  it("is a pure function — same token always returns same value", () => {
+    for (let i = 0; i < 5; i++) {
+      expect(cssVar("accent")).toBe("var(--color-accent)");
+      expect(cssVar("surface")).toBe("var(--color-surface)");
+      expect(cssVar("good")).toBe("var(--color-good)");
+    }
+  });
+
+  it("handles hyphenated tokens correctly", () => {
+    expect(cssVar("surface-elevated")).toBe("var(--color-surface-elevated)");
+    expect(cssVar("line-soft")).toBe("var(--color-line-soft)");
+    expect(cssVar("ink-mute")).toBe("var(--color-ink-mute)");
+  });
+
+  it("produces a value usable as an inline style prop value", () => {
+    // cssVar returns a plain string, which is exactly what style={{ color: cssVar(token) }}
+    // expects — no extra wrapping needed.
+    const result = cssVar("accent");
+    expect(typeof result).toBe("string");
+    expect(result.startsWith("var(--color-")).toBe(true);
+    expect(result.endsWith(")")).toBe(true);
+  });
+});

workspace-server/internal/handlers/plugins_sources_test.go

@@ -0,0 +1,54 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+// ListSources is the only exported function in plugins_sources.go. It calls
+// h.sources.Schemes() and returns the result verbatim, so the test verifies
+// the handler correctly serialises whatever the real registry provides.
+func TestListSources_ReturnsSchemes(t *testing.T) {
+	// Use a real handler — the registry is deterministic (local + github).
+	h := NewPluginsHandler(t.TempDir(), nil, nil)
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest("GET", "/plugins/sources", nil)
+
+	h.ListSources(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+
+	var body struct {
+		Schemes []string `json:"schemes"`
+	}
+	if err := json.Unmarshal(w.Body.Bytes(), &body); err != nil {
+		t.Fatalf("failed to unmarshal response: %v", err)
+	}
+
+	// The default registry registers local + github resolvers.
+	if len(body.Schemes) < 1 {
+		t.Fatalf("expected at least 1 scheme, got %d: %v", len(body.Schemes), body.Schemes)
+	}
+
+	// Verify the schemes slice is stable (same call always returns same result).
+	w2 := httptest.NewRecorder()
+	c2, _ := gin.CreateTestContext(w2)
+	c2.Request = httptest.NewRequest("GET", "/plugins/sources", nil)
+	h.ListSources(c2)
+
+	var body2 struct {
+		Schemes []string `json:"schemes"`
+	}
+	json.Unmarshal(w2.Body.Bytes(), &body2)
+	if len(body.Schemes) != len(body2.Schemes) {
+		t.Errorf("Schemes() is not stable: first=%v, second=%v", body.Schemes, body2.Schemes)
+	}
+}