fix(scripts): drop rich import from analysis scripts (red CI after rich removal)

The cli refactor dropped rich from dependencies, but four scripts still did
`from rich.console import Console` / `rich.table import Table`. Their test
modules import the scripts, so a clean `uv sync --frozen` (CI: core+dev, no
rich) failed at collection with ModuleNotFoundError on macOS/Windows/Linux.

Add a shared plain-text shim `scripts/_plain_console.py` (Console/Table via
click.echo, markup stripped) and switch all four scripts to it. Verified: all
four import with rich blocked, and tests/test_synthid_corpus.py +
tests/test_synthid_pixel_probe.py pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/synthid_pixel_probe.py

@@ -30,8 +30,8 @@ from typing import TYPE_CHECKING
 
 import click
 import numpy as np
+from _plain_console import Console
 from PIL import Image
-from rich.console import Console
 
 if TYPE_CHECKING:
     from numpy.typing import NDArray