refactor: split the repo into self-contained validator, directory, quickstart, spec and site folders

validator/ holds mewslint (lint, css, fetch, DTD/CSS data); directory/ holds
the mews.page service (app, db, check, pages, cli) and depends on validator/;
quickstart/ holds mews-quickstart and md2mews.py for third parties who want
to create Mews content without cloning the repo; spec/ consolidates doc/ and
dtd/ with the canonical mews-0.1.css; site/ becomes a Pelican project with
the forward-facing pages as Markdown, the check form kept as a raw HTML
snippet. Root pyproject.toml is now a virtual uv workspace over validator,
directory and quickstart, with cross-cutting tests that span more than one
of them staying at the repo root. Makefile and flake.nix updated to match.

validator/tests/test_css.py

@@ -0,0 +1,60 @@
+"""The section 5.2 comparison: an unmodified copy, plus added @font-face rules."""
+
+from importlib import resources
+
+from mews import css
+
+CANONICAL = resources.files("mews.data").joinpath("mews-0.1.css").read_text("utf-8")
+
+FONT_FACE = """@font-face {
+  font-family: "Atkinson Hyperlegible";
+  src: url(/fonts/atkinson.woff2) format("woff2");
+}
+
+"""
+
+
+def test_an_unmodified_copy_passes():
+    assert css.compare(CANONICAL).equal
+
+
+def test_line_endings_and_trailing_spaces_do_not_matter():
+    mangled = CANONICAL.replace("\n", "   \r\n") + "\n\n\n"
+    assert css.compare(mangled).equal
+
+
+def test_an_added_font_face_passes_and_is_read():
+    result = css.compare(FONT_FACE + CANONICAL)
+    assert result.equal
+    assert result.font_urls == ["/fonts/atkinson.woff2"]
+
+
+def test_a_font_face_at_the_end_also_passes():
+    assert css.compare(CANONICAL + "\n" + FONT_FACE).equal
+
+
+def test_a_changed_rule_fails_with_a_line_number():
+    result = css.compare(CANONICAL.replace("#faf8f3", "#ffffff"))
+    assert not result.equal
+    assert result.diff_line == 5
+    assert "background-color" in result.diff
+
+
+def test_a_reordered_rule_fails():
+    lines = CANONICAL.split("\n")
+    swapped = "\n".join([*lines[:4], lines[5], lines[4], *lines[6:]])
+    assert not css.compare(swapped).equal
+
+
+def test_a_removed_rule_fails():
+    assert not css.compare(CANONICAL.replace("hr {", "hr-off {")).equal
+
+
+def test_an_import_is_noticed():
+    assert css.compare('@import url("x.css");\n' + CANONICAL).has_import
+
+
+def test_a_font_face_inside_a_media_query_is_not_stripped():
+    inner = "@media screen {\n" + FONT_FACE + "}\n"
+    result = css.compare(CANONICAL + inner)
+    assert not result.equal