chore(release): 1.0.0b1 — the v1 target, staged as a beta

All seven v1 capabilities are landed (ROADMAP's v1 target is met), so this is
the first release of the 1.x train. Staged as a beta rather than cut final on
the operator's call: per the canonical policy `-beta.N` means feature-complete,
external testing, no new features, focus is on bugs — which is exactly this
state, with a cross-frontier bug-hunt panel outstanding on U7's diff.

The repo learned this sequencing the hard way once: v0.2.0 was tagged and
announced while a contract panel was in flight, the panel found three defects in
the code just released, and v0.2.1 shipped within the hour. A beta is the
designed answer to that, not a workaround for it.

ALSO FIXES A SECOND COPY OF THE VERSION, found while cutting this one.
`booth.__version__` was the literal `0.1.0` and had been wrong through six
releases. It is now read from pyproject.toml — deliberately NOT from
importlib.metadata, which describes a different artifact: this repo has no build
step and no install step (booth.service runs uvicorn with WorkingDirectory set
to the tree), and the venv was carrying a vestigial booth-0.3.0.dist-info with
no package directory behind it. Installed metadata therefore reported 0.3.0 for
a tree at 1.0.0b1 — confidently wrong and varying by environment, which is worse
than a literal that at least fails the same way everywhere.

booth/__init__.py is also, it turns out, effectively stdlib-only: scripts/booth
imports booth.links / booth.marks / booth.manifest under the system python3 with
no venv, and every one of those executes the package root first. Nothing
asserted it. test_stdlib_only now covers __init__, and the no-venv import path
is verified under python3.11 reporting 1.0.0b1.

642 tests green.

tests/test_marks.py

@@ -7,6 +7,8 @@ See docs/contracts/u2_marks.contract.md.
 """
 import ast
 import json
+import re
+import tomllib
 import pathlib
 import sys
 
@@ -276,7 +278,7 @@ def test_as_dict_round_trips_through_json(tmp_path):
 # ---- the stdlib-only invariant (INV-5) --------------------------------------
 
 
-@pytest.mark.parametrize("module", ["marks", "asks", "links", "manifest", "benches"])
+@pytest.mark.parametrize("module", ["marks", "asks", "links", "manifest", "benches", "__init__"])
 def test_stdlib_only(module):
     """INV-5. scripts/booth imports these under the system python3 with NO venv,
     through a `python3 -c` heredoc that no AST extractor can see — so nothing
@@ -1428,3 +1430,31 @@ def test_a_healthy_multi_answer_still_hydrates(tmp_path):
     by = {m.id: m for m in marks_for(tmp_path)}
     assert by["multi"].error is None, by["multi"].error
     assert by["single"].error is None, by["single"].error
+
+
+def test_the_package_version_carries_no_literal_of_its_own():
+    """`booth.__version__` said `0.1.0` through six releases while pyproject
+    said `0.6.1` — a second copy of one fact, drifting silently, found only
+    while cutting 1.0.
+
+    THE ASSERTION IS THE ABSENCE OF A LITERAL, not agreement with pyproject:
+    `__version__` is now READ from pyproject, so comparing the two would be
+    circular and would prove only that the read works. The defeating change is
+    hardcoding a number back into this module, and that is what this catches.
+    """
+    src = (pathlib.Path(__file__).parent.parent / "booth" / "__init__.py").read_text()
+    literals = re.findall(r'__version__\s*=\s*["\']([^"\']+)["\']', src)
+    assert not literals, f"booth/__init__.py hardcodes a version again: {literals}"
+
+
+def test_the_package_version_is_the_one_the_tree_declares():
+    """And it resolves, from the tree, to what pyproject says — NOT to whatever
+    a stale dist-info in some venv happens to record. Found saying `0.3.0` from
+    installed metadata while the tree was at `1.0.0b1`."""
+    import booth
+
+    declared = tomllib.loads(
+        (pathlib.Path(__file__).parent.parent / "pyproject.toml").read_text()
+    )["project"]["version"]
+    assert booth.__version__ == declared
+    assert booth.__version__ != "0.0.0+unknown", "the pyproject read fell through"