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

engine/pipeline/params.py

@@ -32,7 +32,7 @@ class PipelineParams:
 
     # Effect config
     effect_order: list[str] = field(
-        default_factory=lambda: ["noise", "fade", "glitch", "firehose", "hud"]
+        default_factory=lambda: ["noise", "fade", "glitch", "firehose"]
     )
     effect_enabled: dict[str, bool] = field(default_factory=dict)
     effect_intensity: dict[str, float] = field(default_factory=dict)
@@ -127,19 +127,19 @@ DEFAULT_HEADLINE_PARAMS = PipelineParams(
     source="headlines",
     display="terminal",
     camera_mode="vertical",
-    effect_order=["noise", "fade", "glitch", "firehose", "hud"],
+    effect_order=["noise", "fade", "glitch", "firehose"],
 )
 
 DEFAULT_PYGAME_PARAMS = PipelineParams(
     source="headlines",
     display="pygame",
     camera_mode="vertical",
-    effect_order=["noise", "fade", "glitch", "firehose", "hud"],
+    effect_order=["noise", "fade", "glitch", "firehose"],
 )
 
 DEFAULT_PIPELINE_PARAMS = PipelineParams(
     source="pipeline",
     display="pygame",
     camera_mode="trace",
-    effect_order=["hud"],  # Just HUD for pipeline viz
+    effect_order=[],  # No effects for pipeline viz
 )