fix: Python 3.8 compatibility

[Copilot]

Two type annotation constructs introduced after Python 3.8 were used at module/function scope, causing TypeError at import time on Python 3.8.

Changes

• sys_deps.py: Add from __future__ import annotations (PEP 563) — defers annotation evaluation so str | None (PEP 604, 3.10+) and list[str] (PEP 585, 3.9+) are never evaluated as expressions at runtime
• parser.py: Use raw strings for regex patterns to eliminate invalid escape sequences (\[, \s) that produce SyntaxWarning
• .github/workflows/python-tests.yml: Add Python 3.8 to the CI test matrix to explicitly verify compatibility going forward

[alaurenzi]

@copilot Add python 3.8 to the test matrix (gh workflow)

[Copilot]

@copilot Add python 3.8 to the test matrix (gh workflow)

Done — added '3.8' to the python-version matrix in .github/workflows/python-tests.yml (commit ci: add Python 3.8 to test matrix).