fix: make installed wheel self-contained + harden install.sh prereqs

Addresses the review on PR #481.

Self-contained wheel (review point 1): the gateway/infra/orchestrator
images build from a context that must hold bot_bottle/, pyproject.toml,
and the root-level Dockerfiles. Modules previously located these by
walking __file__ to the repo root, so an installed wheel (package in
site-packages, no repo root) passed `doctor` but failed `start`.

- Add bot_bottle/resources.py: build_root() returns the repo root in a
  checkout (unchanged) or a staged copy from the wheel's bundled
  _resources/ otherwise; dockerfile()/nix_netpool_module()/
  netpool_script() derive from it.
- setup.py bundles the root Dockerfiles, nix module, netpool script, and
  pyproject.toml into bot_bottle/_resources/ at build; MANIFEST.in ships
  them in the sdist.
- Route every _REPO_ROOT/_REPO_DIR call site (docker/macos launch, macos
  infra, firecracker infra_vm/infra_artifact/setup, orchestrator
  lifecycle/gateway) through resources. Checkout behavior is unchanged.

install.sh prerequisites (review point 2): check for git when installing
a git+ spec, and — before the pip fallback — that pip is usable and the
interpreter isn't externally managed (PEP 668), pointing at pipx.

Tests: test_resources covers checkout + staged-wheel layouts;
test_wheel_install builds the wheel, installs it into an isolated venv,
and asserts `doctor` runs and build_root() yields a valid context.
Running `start` end-to-end still needs a Docker/KVM host (CI).

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

bot_bottle/backend/macos_container/gateway.py

@@ -28,6 +28,7 @@ from ...paths import (
     ORCHESTRATOR_AUTH_JWT_ENV,
     host_gateway_ca_dir,
 )
+from ... import resources
 from .. import util as backend_util
 from . import util as container_mod
 
@@ -52,8 +53,6 @@ GATEWAY_DAEMONS = "egress,git-http,supervise"
 
 GATEWAY_IMAGE = os.environ.get("BOT_BOTTLE_GATEWAY_IMAGE", "bot-bottle-gateway:latest")
 
-_REPO_ROOT = Path(__file__).resolve().parents[3]
-
 
 def ensure_networks(
     network: str = GATEWAY_NETWORK,
@@ -84,14 +83,16 @@ class MacosGateway(Gateway):
         network: str = GATEWAY_NETWORK,
         egress_network: str = GATEWAY_EGRESS_NETWORK,
         control_network: str = CONTROL_NETWORK,
-        repo_root: Path = _REPO_ROOT,
+        repo_root: Path | None = None,
     ) -> None:
         self.image_ref = image_ref
         self.name = name
         self.network = network
         self.egress_network = egress_network
         self.control_network = control_network
-        self._repo_root = repo_root
+        # Build context: the repo root in a checkout, a staged copy from the
+        # installed wheel otherwise (bot_bottle.resources).
+        self._repo_root = repo_root if repo_root is not None else resources.build_root()
         # Set by `connect_to_orchestrator`: the URL the daemons resolve policy
         # against + the pre-minted `gateway` token they present. The gateway
         # never mints, so it never holds the signing key (#469).