feat!: pin Python 3.14 and Unicode 16.0, and make the tools commands

Python and Unicode
- requires-python is >=3.14,<3.15: 3.14 is the only Python with the
  Unicode 16.0 data the specification pins (3.13 has 15.1, 3.15 has 17.0).
- `import paperspec` raises ImportError unless unicodedata reports
  paperspec.UNICODE_VERSION (16.0.0), so a source checkout or an install
  that bypasses requires-python cannot compute values on other data.

Commands
- tools/{check,build,validate,load,stress,site}.py move with history to
  src/paperspec/cli/ and install as paperspec-check, -build, -validate,
  -load, -stress and -site; each also runs as `python -m paperspec.cli.X`.
- paperspec.cli.require() exits with "install paperspec[tools]" when
  cryptography or jsonschema is missing; paperspec.cli.checkout() finds
  the repository the check, build, stress and site commands work on (the
  editable install's own checkout, else the one around the current
  folder) and exits with a message outside one. tools/__init__.py is gone.
- validate and load read the schemas and SQL through the new
  paperspec.resources.path(), which finds them in a wheel and in an
  editable install alike, so they work anywhere the package is installed.
- check runs the rebuild as `python -m paperspec.cli.build`.
- build still writes the provenance tool label "paperspec tools/build.py":
  it is part of every hashed and signed fixture.
- pixi tasks and the check workflow run the commands; tools/README.md
  documents them, and the other docs name the commands instead of paths.

License
- LICENSE.md gives `src/` Apache-2.0 alongside `tools/`. Since the
  previous commit moved the code to src/, no row had covered it.

pixi run check passes (run as `python -m paperspec.cli.check` with src/ on
the path, since this environment cannot install the entry points); the
byte-for-byte rebuild matches, so no fixture or vector changed.
pixi.lock still needs `pixi lock`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pyproject.toml

@@ -10,8 +10,9 @@ readme = "README.md"
 license = "Apache-2.0"
 license-files = ["LICENSE.md"]
 authors = [{ name = "Scientific Computing Studio", email = "maintainer@scient.ing" }]
-# Python 3.14 is the first with the Unicode 16.0 character data the specification pins (spec/01 §1.4).
-requires-python = ">=3.14"
+# Python 3.14 is the only version with the Unicode 16.0 character data the specification pins (spec/01 §1.4);
+# 3.13 has 15.1 and 3.15 has 17.0, and the package refuses to import on either.
+requires-python = ">=3.14,<3.15"
 classifiers = [
     "Development Status :: 3 - Alpha",
     "Intended Audience :: Science/Research",
@@ -28,6 +29,15 @@ schema = ["jsonschema>=4.26", "referencing>=0.35"]
 crypto = ["cryptography>=46"]
 tools = ["paperspec[crypto,schema]"]
 
+# validate and load work wherever the package is installed with [tools]; the other four work on a checkout.
+[project.scripts]
+paperspec-build = "paperspec.cli.build:cli"
+paperspec-check = "paperspec.cli.check:main"
+paperspec-load = "paperspec.cli.load:main"
+paperspec-site = "paperspec.cli.site:main"
+paperspec-stress = "paperspec.cli.stress:main"
+paperspec-validate = "paperspec.cli.validate:main"
+
 [project.urls]
 Homepage = "https://paperspec.scient.ing"
 Repository = "https://git.scient.ing/infra/paperspec"
@@ -38,7 +48,7 @@ Documentation = "https://paperspec.scient.ing/docs/"
 # package as data subpackages, so a consumer reads them with importlib.resources. That mapping is why the
 # packages are listed rather than found.
 [tool.setuptools]
-packages = ["paperspec", "paperspec.schemas", "paperspec.sql", "paperspec.vectors"]
+packages = ["paperspec", "paperspec.cli", "paperspec.schemas", "paperspec.sql", "paperspec.vectors"]
 
 [tool.setuptools.package-dir]
 "" = "src"