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>

tools/validate.py

@@ -1,91 +0,0 @@
-#!/usr/bin/env python3
-"""Validate packages, or run the correction gate on proposals against a package.
-
-Non-normative tooling.
-Usage: python3 tools/validate.py PACKAGE [PACKAGE ...]
-       python3 tools/validate.py --correction PROPOSALS PACKAGE
-A package is a folder, or a zipped package (`.sct.zip`), which is unpacked under the rules of spec/12 §12.2
-before it is checked. Each is checked as spec/22 §22.2 describes, and each failure printed as
-`package: where: rule: message`.
-With --correction, PROPOSALS is a JSON file holding one proposed correction, or a JSON Lines file of several
-applied in order. Each runs through the gate (spec/11 §11.4) against the package's current state, and the record
-it would append to corrections.jsonl is printed, until one is refused. Nothing is written.
-Exit status: 0 when everything is valid, 1 when something is refused, 2 for a usage error.
-"""
-
-import argparse
-import json
-import os
-import sys
-import tempfile
-
-ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-sys.path.insert(0, ROOT)
-import tools  # noqa: E402,F401  checks the runtime and puts src/ first on the path, before paperspec is imported
-
-from paperspec import corrections, jcs, package  # noqa: E402
-from paperspec.schema import Store  # noqa: E402
-from paperspec.tree import Refusal  # noqa: E402
-
-
-def read_proposals(path):
-    with open(path, encoding="utf-8") as f:
-        text = f.read()
-    try:
-        return [json.loads(text)]
-    except json.JSONDecodeError:
-        return [json.loads(ln) for ln in text.splitlines() if ln.strip()]
-
-
-def validate_one(path, store, limit):
-    """The validation report of a package folder or a zipped package."""
-    if package.is_zip(path):
-        return package.validate_zip(path, store, limit=limit)
-    return package.validate(path, store)
-
-
-def main():
-    lines = __doc__.splitlines()
-    ap = argparse.ArgumentParser(description=lines[0], epilog="\n".join(lines[5:]),
-                                 formatter_class=argparse.RawDescriptionHelpFormatter)
-    ap.add_argument("--correction", metavar="PROPOSALS",
-                    help="a JSON or JSON Lines file of proposed corrections to run through the gate")
-    ap.add_argument("--max-size", metavar="BYTES", type=int, default=package.ZIP_LIMIT,
-                    help="refuse a zipped package that expands past this many bytes (default %d)" % package.ZIP_LIMIT)
-    ap.add_argument("packages", nargs="+", metavar="PACKAGE", help="package folders or zipped packages")
-    a = ap.parse_args()
-    if a.correction and len(a.packages) != 1:
-        ap.error("--correction checks proposals against exactly one package")
-    store, bad = Store(os.path.join(ROOT, "schemas")), False
-    for p in a.packages:
-        for e in validate_one(p, store, a.max_size).errors:
-            print("%s: %s: %s: %s" % (p, e["where"], e["rule"], e["message"]), file=sys.stderr)
-            bad = True
-    if bad:
-        return 1
-    if not a.correction:
-        for p in a.packages:
-            print("%s: valid" % p)
-        return 0
-    pkg = a.packages[0]
-    with tempfile.TemporaryDirectory() as tmp:
-        if package.is_zip(pkg):
-            pkg = package.read_zip(pkg, tmp, a.max_size)
-        state = package.read_state(pkg)
-    if any(n.get("withheld") for n in state.nodes):
-        print("%s: doc.policy.withheld: a package that withholds its text takes no corrections" % a.packages[0],
-              file=sys.stderr)
-        return 1
-    for i, proposal in enumerate(read_proposals(a.correction), 1):
-        try:
-            state, record = corrections.gate(state, proposal, store)
-        except Refusal as e:
-            where = "%s:%d" % (a.correction, i) + (" " + e.node if e.node else "")
-            print("%s: %s: %s" % (where, e.rule, e.message), file=sys.stderr)
-            return 1
-        print(jcs.dumps(record))
-    return 0
-
-
-if __name__ == "__main__":
-    sys.exit(main())