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>

bot_bottle/cli/__init__.py

@@ -1,6 +1,6 @@
 """Main CLI dispatcher.
 
-Commands: active, backend, cleanup, commit, edit, init, list, resume, start, supervise
+Commands: active, backend, cleanup, commit, doctor, edit, init, list, resume, start, supervise
 """
 
 from __future__ import annotations
@@ -17,6 +17,7 @@ from .active import cmd_active
 from .backend import cmd_backend
 from .cleanup import cmd_cleanup
 from .commit import cmd_commit
+from .doctor import cmd_doctor
 from .edit import cmd_edit
 from .init import cmd_init
 from .login import cmd_login
@@ -31,6 +32,7 @@ COMMANDS = {
     "backend": cmd_backend,
     "cleanup": cmd_cleanup,
     "commit": cmd_commit,
+    "doctor": cmd_doctor,
     "edit": cmd_edit,
     "init": cmd_init,
     "list": cmd_list,
@@ -45,7 +47,7 @@ COMMANDS = {
 # the host (TAP pool, /dev/kvm, firecracker) and never opens the store, so
 # gating it on the schema breaks preflight on a fresh CI runner where stdin
 # isn't a TTY and the migration prompt can't be answered.
-NO_MIGRATION_COMMANDS = frozenset({"backend", "login"})
+NO_MIGRATION_COMMANDS = frozenset({"backend", "doctor", "login"})
 
 
 def usage() -> None:
@@ -55,6 +57,7 @@ def usage() -> None:
     sys.stderr.write("  backend   set up / check / undo a backend's host prerequisites (setup|status|teardown)\n")
     sys.stderr.write("  cleanup   stop and remove all active bot-bottle containers\n")
     sys.stderr.write("  commit    snapshot a running bottle's container state to a Docker image\n")
+    sys.stderr.write("  doctor    check host prerequisites (Python, backend, config dir)\n")
     sys.stderr.write("  edit      open an agent in vim for editing\n")
     sys.stderr.write("  init      interactively create a new agent and add it to bot-bottle.json\n")
     sys.stderr.write("  list      list available agents from bot-bottle.json\n")