feat: add quick install script and packaging (#197)

Give bot-bottle a real distribution path so new users can install
without cloning the repo:

- pyproject.toml: full project metadata, a `bot-bottle` console-script
  entry point (bot_bottle.cli:main), and package-data for the runtime
  assets (Dockerfiles, egress entrypoint, netpool defaults, macos init).
  Still zero runtime pip dependencies.
- install.sh: POSIX, sudo-free, idempotent bootstrapper — checks Python
  >= 3.11, creates ~/.bot-bottle/{agents,bottles,contrib}, installs via
  pipx (pip --user fallback), then runs `bot-bottle doctor`.
- `bot-bottle doctor`: new store-free subcommand reporting Python
  version, backend availability (reuses is_backend_available rather than
  hardcoding Docker), and config-dir presence. Exits non-zero when a hard
  prerequisite is unmet.
- PRD prd-new-install-script and unit tests for doctor, the packaging
  contract, and the install script.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_pyproject.py

@@ -0,0 +1,45 @@
+"""Unit: pyproject.toml packaging contract.
+
+Guards the install/distribution surface: the console-script entry point,
+the stdlib-only (empty) dependency list, and that every package-data glob
+still points at a file that exists (so an installed wheel isn't missing a
+Dockerfile or entrypoint the runtime reads).
+"""
+
+from __future__ import annotations
+
+import tomllib
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+PYPROJECT = REPO_ROOT / "pyproject.toml"
+
+
+class TestPyproject(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        with PYPROJECT.open("rb") as fh:
+            cls.data = tomllib.load(fh)
+
+    def test_entry_point_targets_cli_main(self):
+        scripts = self.data["project"]["scripts"]
+        self.assertEqual("bot_bottle.cli:main", scripts["bot-bottle"])
+
+    def test_no_runtime_dependencies(self):
+        # AGENTS.md: the package has no runtime pip dependencies.
+        self.assertEqual([], self.data["project"]["dependencies"])
+
+    def test_requires_python_311(self):
+        self.assertEqual(">=3.11", self.data["project"]["requires-python"])
+
+    def test_package_data_files_exist(self):
+        pkg_data = self.data["tool"]["setuptools"]["package-data"]["bot_bottle"]
+        self.assertTrue(pkg_data, "expected package-data entries")
+        for rel in pkg_data:
+            path = REPO_ROOT / "bot_bottle" / rel
+            self.assertTrue(path.is_file(), f"package-data missing: {path}")
+
+
+if __name__ == "__main__":
+    unittest.main()