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/infra.py

@@ -24,6 +24,7 @@ from __future__ import annotations
 
 from pathlib import Path
 
+from ... import resources
 from ...orchestrator.lifecycle import (
     DEFAULT_PORT,
     DEFAULT_STARTUP_TIMEOUT_SECONDS,
@@ -53,8 +54,6 @@ from .orchestrator import (
 # still import it (probe / reprovision attribute against the gateway).
 INFRA_NAME = GATEWAY_NAME
 
-_REPO_ROOT = Path(__file__).resolve().parents[3]
-
 
 class MacosInfraService(InfraService):
     """Composes the per-host orchestrator + gateway containers. Callers use
@@ -70,7 +69,7 @@ class MacosInfraService(InfraService):
         control_network: str = CONTROL_NETWORK,
         gateway_image: str = GATEWAY_IMAGE,
         orchestrator_image: str = ORCHESTRATOR_IMAGE,
-        repo_root: Path = _REPO_ROOT,
+        repo_root: Path | None = None,
         orchestrator_name: str = ORCHESTRATOR_NAME,
         gateway_name: str = INFRA_NAME,
         db_volume: str = ORCHESTRATOR_DB_VOLUME,
@@ -81,7 +80,9 @@ class MacosInfraService(InfraService):
         self.control_network = control_network
         self.gateway_image = gateway_image
         self.orchestrator_image = orchestrator_image
-        self._repo_root = repo_root
+        # Build context / bind-mount source: 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()
         self._orchestrator_name = orchestrator_name
         self._gateway_name = gateway_name
         self._db_volume = db_volume