Deprecate Python 3.6/3.7 and harden property API

[jserv]

This raises the supported floor to 3.8 and prove it in CI. The 3.6 claim was unverifiable: 3.6 (EOL 2021) and 3.7 (EOL 2023) are unavailable on GitHub-hosted runner. Update python_requires, classifiers, Ruff target, and the module/README docs in lockstep, and expand the selftest matrix to run 3.8, 3.10, 3.12, and 3.13 on Linux.

Drop the pre-3.8 shims the bump makes dead: collapse the 4-way copy_fn ladder to os.replace (3.3+) vs copyfile for symlinks, and remove the hasattr(e, "msg") guards around bad-regex reporting (re.error.msg is 3.5+).

Return namedtuples (Range, Default, Select, Imply) for the location-bearing Symbol/Choice property records instead of bare tuples. They are tuple subclasses, so positional unpacking and indexing are unchanged; the named fields add a safer access idiom than remembering positions. Wrap both the parse-time construction and the dependency-propagation reconstruction so the type survives. orig_* stay plain 2-/3-tuples as the stable compat surface.

Add tests/test_ui_ranges.py covering the real _range_info() / _check_valid() range helpers in menuconfig and guiconfig against tests/Krange, guarding the sym.ranges tuple-arity regression that previously had no test.

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Summary by cubic

Raises the minimum Python to 3.8 and switches location-bearing property records to namedtuples for safer access without breaking tuple unpacking. CI now verifies 3.8–3.13 on Linux; new tests cover range helpers to prevent regressions.

• Refactors

  • Set python_requires to 3.8+, update classifiers/docs, set ruff target-version to py38.
  • Expand CI: Linux 3.8/3.10/3.12/3.13; macOS/Windows on 3.12.
  • Replace pre-3.8 shims: use os.replace for backups (symlinks still use copyfile); show regex errors as "Bad regular expression: ".
  • Return Range, Default, Select, Imply namedtuples; preserve types during dependency propagation; add assertions in tests.
  • Add tests/test_ui_ranges.py to exercise _range_info() and _check_valid() and guard tuple-arity issues.

• Migration

  • Requires Python 3.8+.
  • Code unpacking or indexing property records continues to work; you can now use attributes like r.low and d.cond.
  • orig_* properties remain plain 2-/3-tuples and are unchanged.

^{Written for commit cf64994. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 11 files

_{Re-trigger cubic}