fix(packaging): canonical SPDX license expression (0.3.2)

[t0kubetsu]

Problem

pyproject.toml declared license = "GPL-3.0". That is a deprecated SPDX
identifier: setuptools warns on it and PyPI validates license expressions, so the
correct spelling is GPL-3.0-only (or GPL-3.0-or-later). The license itself is
not changing — only its machine-readable form.

The build requirement was also under-constrained at setuptools>=68. This file
already relies on PEP 639 — a string license holding an SPDX expression, plus
license-files — which setuptools only implements from 77. Versions 68-76
reject a string license value, so a build in a clean environment could resolve
a setuptools too old to understand this metadata and fail. It works locally only
because pip's build isolation happens to fetch a current setuptools.

Change

• license = "GPL-3.0-only"
• requires = ["setuptools>=77", "wheel"]
• Version bumped to 0.3.2 in pyproject.toml and the __init__.py fallback
  literal, with the matching CHANGELOG.md section and comparison links.

No source code, API or behaviour changed.

Verification

421 tests passed
ruff check     -> All checks passed!

The equivalent change was verified end-to-end on a built wheel
(License-Expression: GPL-3.0-only, dist-info/licenses/LICENSE present).

Part of an org-wide sweep: every module carried the same deprecated identifier.
Follows quantumvalidator, which shipped this in v0.6.4.

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Review details

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📥 Commits

Reviewing files that changed from the base of the PR and between 3394ebf and 1eba768.

📒 Files selected for processing (3)

• CHANGELOG.md
• headersvalidator/__init__.py
• pyproject.toml

---

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[greptile-apps]

Greptile Summary

Updates the package metadata for release 0.3.2 without changing runtime behavior.

• Replaces the deprecated GPL identifier with the canonical GPL-3.0-only SPDX expression.
• Raises the setuptools build requirement to the first release supporting the declared PEP 639 metadata.
• Synchronizes the project and fallback versions and documents the release in the changelog.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The packaging requirements match the PEP 639 metadata, the license expression remains consistent with the repository license, and all release-version references are synchronized.

Important Files Changed

Filename	Overview
pyproject.toml	Correctly updates the release version, canonical SPDX expression, and compatible setuptools minimum.
headersvalidator/init.py	Keeps the source-checkout fallback version synchronized with package metadata.
CHANGELOG.md	Adds a correctly formatted 0.3.2 entry and updates comparison links consistently.

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