fix: wire allowed_tools/disallowed_tools inputs through to Claude SDK

The disallowed tools env var read in run.ts was DISALLOWED_TOOLS_INPUT
(raw user input) instead of DISALLOWED_TOOLS (computed value including
WebSearch/WebFetch defaults). This meant default tool disallowance was
never enforced. Also removes orphaned ALLOWED_TOOLS env var export from
createPrompt() (tag mode passes allowed tools via claudeArgs instead),
extracts shared parseToolsInput utility to eliminate duplication, and
adds tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test/utils/parse-tools-input.test.ts

@@ -0,0 +1,43 @@
+import { describe, test, expect } from "bun:test";
+import { parseToolsInput } from "../../src/utils/parse-tools-input";
+
+describe("parseToolsInput", () => {
+  test("returns empty array for undefined", () => {
+    expect(parseToolsInput(undefined)).toEqual([]);
+  });
+
+  test("returns empty array for empty string", () => {
+    expect(parseToolsInput("")).toEqual([]);
+  });
+
+  test("parses single tool", () => {
+    expect(parseToolsInput("WebSearch")).toEqual(["WebSearch"]);
+  });
+
+  test("parses comma-separated tools", () => {
+    expect(parseToolsInput("WebSearch,WebFetch")).toEqual([
+      "WebSearch",
+      "WebFetch",
+    ]);
+  });
+
+  test("trims whitespace around tools", () => {
+    expect(parseToolsInput(" WebSearch , WebFetch ")).toEqual([
+      "WebSearch",
+      "WebFetch",
+    ]);
+  });
+
+  test("filters empty entries from trailing commas", () => {
+    expect(parseToolsInput("WebSearch,,WebFetch,")).toEqual([
+      "WebSearch",
+      "WebFetch",
+    ]);
+  });
+
+  test("handles tool patterns with special characters", () => {
+    expect(
+      parseToolsInput("Bash(npm test:*),mcp__github_ci__get_ci_status"),
+    ).toEqual(["Bash(npm test:*)", "mcp__github_ci__get_ci_status"]);
+  });
+});