feat(manifest): add git_user bottle field (issue #86)

Per-bottle `git config --global user.name` / `user.email` pair
so the agent's commits inside the bottle land with a known
identity rather than the agent image's default (no user, or
whatever the image dropped in).

Schema:
  git_user:
    name: "Eric Bauerfeld"
    email: "eric+claude@dideric.is"

Either field can be set independently — name-only / email-only
configs are valid and apply just the field that's set. An
explicit `git_user:` block with both fields empty dies at parse
time rather than silently no-op'ing; an omitted block is the
no-op path (default GitUser is empty, provisioner skips).

Parse-time validation:
- Unknown sub-keys die (e.g., typo of `username`).
- Non-string name/email dies.
- Both-empty dies (half-finished edit hint).

11 unit tests in `test_manifest_git_user.py`; 653 unit tests pass.

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

tests/unit/test_manifest_git_user.py

@@ -0,0 +1,109 @@
+"""Unit: Bottle.git_user manifest parsing + validation (issue #86)."""
+
+import contextlib
+import io
+import unittest
+
+from claude_bottle.log import Die
+from claude_bottle.manifest import GitUser, Manifest
+
+
+def _die_message(callable_, *args, **kwargs) -> str:
+    """Run `callable_` expecting it to die, return the stderr text
+    so tests can assert specifics. `die()` prints to stderr then
+    raises Die(1) — the exit code is in the exception, the human
+    message is in stderr."""
+    buf = io.StringIO()
+    with contextlib.redirect_stderr(buf):
+        try:
+            callable_(*args, **kwargs)
+        except Die:
+            return buf.getvalue()
+    raise AssertionError("expected Die was not raised")
+
+
+def _manifest(git_user):
+    return {
+        "bottles": {"dev": {"git_user": git_user}},
+        "agents": {"demo": {"skills": [], "prompt": "", "bottle": "dev"}},
+    }
+
+
+class TestGitUserParsing(unittest.TestCase):
+    def test_parses_both_fields(self):
+        m = Manifest.from_json_obj(_manifest({
+            "name": "Eric Bauerfeld",
+            "email": "eric+claude@dideric.is",
+        }))
+        u = m.bottles["dev"].git_user
+        self.assertEqual("Eric Bauerfeld", u.name)
+        self.assertEqual("eric+claude@dideric.is", u.email)
+        self.assertFalse(u.is_empty())
+
+    def test_name_only(self):
+        m = Manifest.from_json_obj(_manifest({"name": "Bot"}))
+        u = m.bottles["dev"].git_user
+        self.assertEqual("Bot", u.name)
+        self.assertEqual("", u.email)
+
+    def test_email_only(self):
+        m = Manifest.from_json_obj(_manifest({"email": "bot@example.com"}))
+        u = m.bottles["dev"].git_user
+        self.assertEqual("", u.name)
+        self.assertEqual("bot@example.com", u.email)
+
+    def test_omitted_defaults_to_empty(self):
+        # No git_user block at all → empty GitUser, is_empty True →
+        # provisioner skips the `git config` step entirely.
+        m = Manifest.from_json_obj({
+            "bottles": {"dev": {}},
+            "agents": {"demo": {"skills": [], "prompt": "", "bottle": "dev"}},
+        })
+        u = m.bottles["dev"].git_user
+        self.assertTrue(u.is_empty())
+
+    def test_both_empty_strings_dies(self):
+        # An explicit `git_user: {name: "", email: ""}` is a typo
+        # /  half-finished edit; fail loudly rather than silently
+        # no-op (the operator clearly meant to configure something).
+        msg = _die_message(
+            Manifest.from_json_obj, _manifest({"name": "", "email": ""}),
+        )
+        self.assertIn("neither name nor email", msg)
+
+    def test_unknown_key_dies(self):
+        msg = _die_message(
+            Manifest.from_json_obj,
+            _manifest({"name": "Bot", "username": "bot"}),
+        )
+        self.assertIn("unknown key", msg)
+        self.assertIn("username", msg)
+
+    def test_non_string_name_dies(self):
+        msg = _die_message(
+            Manifest.from_json_obj, _manifest({"name": 42}),
+        )
+        self.assertIn("git_user.name must be a string", msg)
+
+    def test_non_string_email_dies(self):
+        msg = _die_message(
+            Manifest.from_json_obj, _manifest({"email": ["x@y.z"]}),
+        )
+        self.assertIn("git_user.email must be a string", msg)
+
+
+class TestGitUserDirect(unittest.TestCase):
+    """Direct GitUser dataclass exercises (no manifest wrapper)."""
+
+    def test_is_empty_default(self):
+        self.assertTrue(GitUser().is_empty())
+
+    def test_is_empty_false_when_name_set(self):
+        self.assertFalse(GitUser(name="x").is_empty())
+
+    def test_is_empty_false_when_email_set(self):
+        self.assertFalse(GitUser(email="x@y").is_empty())
+
+
+if __name__ == "__main__":
+    unittest.main()