Wrap the README banner in a code fence so it renders as typed (#1403)

The decorative banner under the title wasn't in a fenced code block, so GitHub's
markdown collapsed its leading whitespace and joined the box-drawing rules,
rendering the ASCII art misaligned instead of monospace-as-typed (issue #1390).
Fence it; the H1 title stays a real heading.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -1,7 +1,10 @@
 # Odysseus
+
+```
 ───────────────────────────────────────────────
  ⊹ ࣪ ˖ ૮( ˶ᵔ ᵕ ᵔ˶ )っ  Odysseus vers. 1.0
 ───────────────────────────────────────────────
+```
 
 ![Odysseus](docs/odysseus.jpg)
 

tests/test_readme_ascii_fenced.py

@@ -0,0 +1,34 @@
+"""Regression guard for issue #1390 — the README banner / ASCII art was not in a
+fenced code block, so GitHub's markdown collapsed its leading whitespace and the
+box-drawing rules, rendering it misaligned instead of monospace-as-typed.
+
+This pins that the decorative banner stays inside a ``` code fence.
+"""
+from pathlib import Path
+
+README = Path(__file__).resolve().parent.parent / "README.md"
+
+# Distinctive bits of the banner (box-drawing rule + the kaomoji version line).
+_RULE = "─" * 10
+_BANNER_LINE = "Odysseus vers. 1.0"
+
+
+def _fenced_segments(text: str):
+    """Return the segments of *text* that sit INSIDE ``` fences."""
+    parts = text.split("```")
+    # parts[0] is before the first fence, parts[1] is inside the first fence, ...
+    return parts[1::2]
+
+
+def test_readme_banner_is_inside_a_code_fence():
+    text = README.read_text(encoding="utf-8")
+    assert _BANNER_LINE in text, "banner line missing from README"
+    inside = "\n".join(_fenced_segments(text))
+    assert _BANNER_LINE in inside, "banner version line must be inside a ``` code fence"
+    assert _RULE in inside, "banner rule line must be inside a ``` code fence"
+
+
+def test_readme_title_stays_a_heading():
+    # The H1 must remain a real heading, not get swallowed into the fence.
+    first = README.read_text(encoding="utf-8").splitlines()[0]
+    assert first.strip() == "# Odysseus"