feat(P01): pyproject entry point + package discovery (REQ-324, cli-engineer)

- [project.scripts] nova = "nova.cli:main"
- [tool.setuptools.packages.find] includes nova, core, adapters
- requires-python bumped to >=3.12
- new `identity` extra (argon2-cffi, cryptography, pyjwt)
- hypothesis>=6.100.0 added to `test` extra
- fix build-backend to setuptools.build_meta (was non-existent
  setuptools.backends._legacy:_Backend — entry-point install was broken)
- ignore .venv/ + nova.egg-info/ workspace artifacts

---ci---
project: acdl
phase: 1
milestone: v1.28
status: execute
persona: cli-engineer
---/ci---

pyproject.toml

@@ -2,19 +2,28 @@
 name = "nova"
 version = "1.14.0"
 description = "Nova — consumers declare intent; the platform delivers safe production deployment."
-requires-python = ">=3.10"
+requires-python = ">=3.12"
 dependencies = [
     "boto3>=1.34",
     "jsonschema>=4.20",
     "pyyaml>=6.0",
 ]
 
+[project.scripts]
+nova = "nova.cli:main"
+
 [project.optional-dependencies]
 test = [
     "pytest>=8.0",
     "pytest-cov>=4.0",
     "pytest-json-report>=1.5",
     "moto[dynamodb]>=5.0",
+    "hypothesis>=6.100.0",
+]
+identity = [
+    "argon2-cffi>=23.1.0",
+    "cryptography>=42.0.0",
+    "pyjwt>=2.8.0",
 ]
 slides = ["python-pptx>=0.6.23"]
 
@@ -34,4 +43,8 @@ run.source = ["core", "adapters"]
 
 [build-system]
 requires = ["setuptools>=68"]
-build-backend = "setuptools.backends._legacy:_Backend"
+build-backend = "setuptools.build_meta"
+
+[tool.setuptools.packages.find]
+where = ["."]
+include = ["nova", "nova.*", "core", "core.*", "adapters.*"]