chore: user-agnostic Claude identity and tests

- Use ~/Clawd instead of hardcoded /Users/steipete/clawd
- Add MEDIA: syntax instructions to identity prefix
- Update tests to check for 'scratchpad' instead of specific path

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/index.core.test.ts

@@ -895,7 +895,7 @@ describe("config and templating", () => {
     const argv = runSpy.mock.calls[0][0];
     expect(argv[0]).toBe("claude");
     expect(argv.at(-1)).toContain("You are Clawd (Claude)");
-    expect(argv.at(-1)).toContain("/Users/steipete/clawd");
+    expect(argv.at(-1)).toContain("scratchpad");
     expect(argv.at(-1)).toMatch(/hi$/);
     // The helper should auto-add print and output format flags without disturbing the prompt position.
     expect(argv.includes("-p") || argv.includes("--print")).toBe(true);
@@ -963,7 +963,7 @@ describe("config and templating", () => {
     expect(result?.text).toBe("Sure! What's up?");
     const argv = runSpy.mock.calls[0][0];
     expect(argv.at(-1)).toContain("You are Clawd (Claude)");
-    expect(argv.at(-1)).toContain("/Users/steipete/clawd");
+    expect(argv.at(-1)).toContain("scratchpad");
   });
 
   it("serializes command auto-replies via the queue", async () => {