fix(onboarding): warn about public forks at the point of decision (#345) (#348)

The quick start walked a new user into gh repo fork - forks of public
repos are always public - and two steps later had /setup write personal
data into tracked files, with the only complete warning in SETUP.md
section 8, a section about pulling updates that a first-time user has no
reason to open during onboarding. A real user hit exactly this (#345).

The warning now sits adjacent to both fork commands (README step 1,
SETUP.md section 2, both pointing at section 8's private-remote recipe),
and /setup checks the origin's visibility BEFORE writing anything: a
public-fork origin gets a confirm-first warning instead of a note after
every file is on disk. A private origin, no origin, or a non-git
directory continues silently. Reported by @basilevs with a complete
reproduction and fix analysis; this implements his fixes (1) and (4).

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/test_onboarding_privacy.py

@@ -0,0 +1,85 @@
+"""Guards for the onboarding privacy warnings (issue #345).
+
+The README's quick start walks a new user into creating a public fork
+(forks of public repos cannot be private) and then has /setup write
+personal data into tracked files, with the only complete warning sitting
+in SETUP.md section 8 - a section about pulling updates, downstream of
+the decision it should inform. A real user hit exactly this. These tests
+pin that the warning lives at the point of decision (adjacent to both
+fork commands) and that /setup checks the origin's visibility BEFORE
+writing anything, not in its closing notes.
+"""
+import re
+import unittest
+from pathlib import Path
+
+REPO = Path(__file__).resolve().parent.parent
+README = REPO / "README.md"
+SETUP_GUIDE = REPO / "SETUP.md"
+SETUP_COMMAND = REPO / ".claude" / "commands" / "setup.md"
+
+
+def section(text: str, heading: str) -> str:
+    """Body of a markdown section up to the next heading of the same level."""
+    level = heading.split(" ")[0]
+    pattern = re.compile(
+        rf"^{re.escape(heading)}\n(.*?)(?=^{level} |\Z)", re.MULTILINE | re.DOTALL
+    )
+    match = pattern.search(text)
+    return match.group(1) if match else ""
+
+
+class TestForkWarningsAtTheDecisionPoint(unittest.TestCase):
+    def assert_warns(self, body: str, where: str):
+        self.assertRegex(
+            body,
+            re.compile(r"public", re.IGNORECASE),
+            f"{where}'s fork section must say the fork will be public",
+        )
+        self.assertIn(
+            "personal data",
+            body,
+            f"{where}'s fork section must say /setup writes personal data into tracked files",
+        )
+        self.assertRegex(
+            body,
+            re.compile(r"section 8|§8|#8-pulling", re.IGNORECASE),
+            f"{where}'s fork section must point at SETUP.md section 8's private-remote recipe",
+        )
+
+    def test_readme_quick_start_warns_next_to_the_fork_command(self):
+        body = section(README.read_text(encoding="utf-8"), "### 1. Fork and clone")
+        self.assertIn("gh repo fork", body, "sanity: the fork command lives in this section")
+        self.assert_warns(body, "README")
+
+    def test_setup_guide_warns_next_to_the_fork_command(self):
+        body = section(SETUP_GUIDE.read_text(encoding="utf-8"), "## 2. Fork and clone")
+        self.assertIn("gh repo fork", body, "sanity: the fork command lives in this section")
+        self.assert_warns(body, "SETUP.md")
+
+
+class TestSetupChecksOriginBeforeWriting(unittest.TestCase):
+    def test_preflight_exists_and_precedes_profile_generation(self):
+        text = SETUP_COMMAND.read_text(encoding="utf-8")
+        self.assertIn(
+            "git remote get-url origin",
+            text,
+            "/setup must check where the working copy would publish to",
+        )
+        preflight_at = text.index("git remote get-url origin")
+        writes_at = text.index("## Step 3: Generate Profile Files")
+        self.assertLess(
+            preflight_at,
+            writes_at,
+            "the origin check must run before any profile file is written - the "
+            "existing Step 4 note fires after everything is already on disk",
+        )
+        self.assertIn(
+            "public",
+            text[max(0, preflight_at - 2000) : preflight_at + 2000].lower(),
+            "the preflight must be about public visibility, not just remote presence",
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()