fix: resolve terminal display wobble and effect dimension stability

- Fix TerminalDisplay: add screen clear each frame (cursor home + erase down)
- Fix CameraStage: use set_canvas_size instead of read-only viewport properties
- Fix Glitch effect: preserve visible line lengths, remove cursor positioning
- Fix Fade effect: return original line when fade=0 instead of empty string
- Fix Noise effect: use input line length instead of terminal_width
- Remove HUD effect from all presets (redundant with border FPS display)
- Add regression tests for effect dimension stability
- Add docs/ARCHITECTURE.md with Mermaid diagrams
- Add mise tasks: diagram-ascii, diagram-validate, diagram-check
- Move markdown docs to docs/ (ARCHITECTURE, Refactor, hardware specs)
- Remove redundant requirements files (use pyproject.toml)
- Add *.dot and *.png to .gitignore

Closes #25

scripts/validate-diagrams.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+"""Validate Mermaid diagrams in markdown files."""
+
+import glob
+import re
+import sys
+
+
+# Diagram types that are valid in Mermaid
+VALID_TYPES = {
+    "flowchart",
+    "graph",
+    "classDiagram",
+    "sequenceDiagram",
+    "stateDiagram",
+    "stateDiagram-v2",
+    "erDiagram",
+    "gantt",
+    "pie",
+    "mindmap",
+    "journey",
+    "gitGraph",
+    "requirementDiagram",
+}
+
+
+def extract_mermaid_blocks(content: str) -> list[tuple[int, str]]:
+    """Extract mermaid blocks with their positions."""
+    blocks = []
+    for match in re.finditer(r"```mermaid\n(.*?)\n```", content, re.DOTALL):
+        blocks.append((match.start(), match.group(1)))
+    return blocks
+
+
+def validate_block(block: str) -> bool:
+    """Check if a mermaid block has a valid diagram type."""
+    if not block.strip():
+        return True  # Empty block is OK
+    first_line = block.strip().split("\n")[0]
+    return any(first_line.startswith(t) for t in VALID_TYPES)
+
+
+def main():
+    md_files = glob.glob("docs/*.md")
+
+    errors = []
+    for filepath in md_files:
+        content = open(filepath).read()
+        blocks = extract_mermaid_blocks(content)
+
+        for i, (_, block) in enumerate(blocks):
+            if not validate_block(block):
+                errors.append(f"{filepath}: invalid diagram type in block {i + 1}")
+
+    if errors:
+        for e in errors:
+            print(f"ERROR: {e}")
+        sys.exit(1)
+
+    print(f"Validated {len(md_files)} markdown files - all OK")
+
+
+if __name__ == "__main__":
+    main()