refactor: move the reference implementation to src/paperspec

The oracle had two import names, `tools.oracle` for the tools and
`paperspec` for other repositories, which could load the same code twice
in one process and needed a gate keyed on the module name. It now lives
in the standard src layout under its one name.

- git mv tools/oracle -> src/paperspec; the 22 rule modules are unchanged.
- The tools import `paperspec`. `tools/__init__.py` now holds the Python
  3.14 and cryptography/jsonschema check and puts src/ first on sys.path,
  so the tools run this checkout's code with or without pixi. The
  package's own __init__ checks nothing and exposes __version__.
- pyproject.toml: version from git tags via setuptools-scm
  (guess-next-dev, node-and-timestamp, src/paperspec/_version.py,
  gitignored). The packages stay listed rather than found because
  schemas/, sql/ and vectors/ stay at the root: the spec links to them and
  the site serves the schemas at their $id URLs.
- pixi.toml: a `dev` feature and environment with setuptools,
  setuptools-scm and python-build, and `pixi run -e dev wheel`.
- check.py scans src/paperspec for rule IDs; README, CONTRIBUTING, the
  FAQ, the overview, the vectors and tools READMEs and the changelog point
  at the new path. The FAQ no longer says the oracle is not a library.

pixi.lock is not re-solved in this commit: with a dynamic version, pixi
builds the package metadata to lock, which needs the conda environment
installed. Run `pixi lock` and commit the result before pushing; the site
workflow installs with --locked.

pixi run check passes; no computed value, vector, fixture, schema or SQL
file changed.

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

tools/build.py

@@ -20,18 +20,19 @@ from fractions import Fraction
 
 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 tools.oracle import align as AL  # noqa: E402
-from tools.oracle import anchors as AN  # noqa: E402
-from tools.oracle import corrections as CO  # noqa: E402
-from tools.oracle import crypto, fingerprint as FP, grade as GR, hashing, jcs, receipts as RC, rights as RI  # noqa: E402
-from tools.oracle import keys as K, log as LG, mldsa, targets as TG, vrf  # noqa: E402
-from tools.oracle.model import LEAVES, MATH_KINDS, RUN_KINDS, VERBATIM_KINDS, Doc  # noqa: E402
-from tools.oracle.notation import fold_math  # noqa: E402
-from tools.oracle.package import ZIP_EXTENSION, history_items, jsonl, line, witness_id, write, write_zip  # noqa: E402
-from tools.oracle.schema import Store  # noqa: E402
-from tools.oracle.text import letter_first, mint_node_id, norm, record_id, sha256_hex  # noqa: E402
-from tools.oracle.tree import Refusal, _flatten, mint_ids, validate_structure  # noqa: E402
+from paperspec import align as AL  # noqa: E402
+from paperspec import anchors as AN  # noqa: E402
+from paperspec import corrections as CO  # noqa: E402
+from paperspec import crypto, fingerprint as FP, grade as GR, hashing, jcs, receipts as RC, rights as RI  # noqa: E402
+from paperspec import keys as K, log as LG, mldsa, targets as TG, vrf  # noqa: E402
+from paperspec.model import LEAVES, MATH_KINDS, RUN_KINDS, VERBATIM_KINDS, Doc  # noqa: E402
+from paperspec.notation import fold_math  # noqa: E402
+from paperspec.package import ZIP_EXTENSION, history_items, jsonl, line, witness_id, write, write_zip  # noqa: E402
+from paperspec.schema import Store  # noqa: E402
+from paperspec.text import letter_first, mint_node_id, norm, record_id, sha256_hex  # noqa: E402
+from paperspec.tree import Refusal, _flatten, mint_ids, validate_structure  # noqa: E402
 
 VERSION = "0.1.0"
 STORE = "smithlab"
@@ -903,7 +904,7 @@ def vectors(out, hale, tiny):
                             ("astral", [T("Let "), M("\U0001d465"), T(" vary with "), M("\U0001d466"), T(".")], [4, 7])]:
         doc, s = sentence_doc(runs)
         p = hashing.plain(doc, s)
-        from tools.oracle.text import cp_to_utf16
+        from paperspec.text import cp_to_utf16
         off.append({"id": cid, "runs": runs, "plain": p, "span": span, "exact": p[span[0]:span[1]],
                     "utf16_span": [cp_to_utf16(p, span[0]), cp_to_utf16(p, span[1])], "code_points": len(p),
                     "utf16_units": cp_to_utf16(p, len(p))})