Re-enable linter in CI by configuring ruff for existing codebase

[Copilot]

The linter was disabled in CI due to 698 errors. Rather than refactoring working code, configured ruff to match the codebase's existing conventions.

Changes

• Auto-fixed 127 errors - Import sorting, whitespace, type hints (Optional[X] → X | None)
• Added ruff configuration - Suppressed 60+ style rules incompatible with existing patterns (print statements, f-strings in logging, mutable defaults, exception chaining, etc.)
• Updated Python minimum to 3.10 - Codebase uses match statements, but pyproject.toml declared >=3.9
• Re-enabled hatch fmt --check in CI - Now enforces consistent style going forward

Rationale

The goal is preventing new style drift, not rewriting existing code. Rules like T201 (print statements), B006 (mutable defaults), and TRY003 (exception messages) flag legitimate patterns used throughout the codebase. Suppressing these at the project level is more pragmatic than mass refactoring.

Per-file ignores added for:

• release_tools/* - Scripts don't need __init__.py
• src/seclab_taskflow_agent/mcp_servers/* - Dynamically loaded modules
• tests/* - Allow assertions

Linter now passes with 0 errors and will catch future issues.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Fix linter errors</issue_title>
<issue_description>I switched off the linter because it produces 100s of error messages:

seclab-taskflow-agent/.github/workflows/ci.yml

Line 38 in d4d4acd

# hatch fmt --check

We should fix those errors (or find a way to suppress them if they're uninteresting), so that we can switch the check on.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Fix linter errors #83

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