Code style checker, agent_check, and source-hygiene CI

[trailcode]

Summary

• Add scripts/code_style_check.py for docs/ezycad_code_style.md rules clang-format does not enforce (vertical rhythm / blank lines first).
• Add scripts/agent_check.py so agents and CI run ASCII + style in one Python process. Markdown table --check runs when .md paths are given.
• CMake: IDE glob for scripts plus ezycad_agent_check target.
• Prefer bool ok = false; over brace-init for clang-format = alignment.
• Apply missing blank lines in src/ and tests/ so the checker is clean.
• Source hygiene CI runs python scripts/agent_check.py.

Closes #253

Related: #229

Test plan

• python scripts/code_style_check.py src tests (no findings)
• Source hygiene workflow on this PR (Windows, Python 3.13)
• Reconfigure CMake to see ezycad_agent_check and scripts/ in the IDE
• Note: python scripts/agent_check.py also flags existing non-ASCII in src/ if any remain (e.g. pi). align_md_tables.py --check is not in CI yet (several docs tables still unaligned).

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Note

Low Risk
Changes are mostly tooling, docs, and formatting; CI still enforces ASCII only, with no runtime or security-sensitive logic changes in the application.

Overview
Introduces scripts/agent_check.py as the single post-edit entry point: 7-bit ASCII on src/ and tests/ (default), optional Markdown table alignment when .md paths are passed, and optional --style to run the new checker. scripts/code_style_check.py enforces vertical rhythm blank-line rules from docs/ezycad_code_style.md (not CI).

Source hygiene CI drops check-nonascii-src.cmd in favor of Python 3.13 + PYTHONUTF8 and python scripts/agent_check.py. CMake adds an ezycad_agent_check IDE target and surfaces the scripts in the solution.

Agent docs, local-dev, release, and the code style guide now point at agent_check.py; the guide also prefers = initialization over brace-init so clang-format can align assignments.

src/ and tests/ get widespread blank-line-only edits so the optional style checker is clean, plus a few ASCII comment fixes in tests (e.g. deg, pi).

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