fix: backport JAR-bundling + release-workflow fixes to 2.0 (#284, #289, #290, #292)

[rahlk]

Backports the JAR-bundling and release-workflow fixes from main to the 2.0 line. 2.0.0-rc.1
shipped jarless (188 KB wheel, no codeanalyzer-java JAR — same class of bug as 1.2.0–1.4.3), so
CLDK.java(...) after a plain pip install failed with codeanalyzer jar not found.

What's ported

Fix	Origin
[tool.hatch.build] artifacts force-includes the JAR (hatchling drops it via the root *.jar ignore, ignoring the nested negation)	#284 / #285
Pipe-safe release guard — fails a jarless build before publishing	#284 / #287
Release notes sourced from CHANGELOG.md + fail-on-blank; label-based scraper and release_config.json removed	#289
Remove obsolete native-binary test + unused import sys	#290
Fix stale conftest docstring for the retired native binary	#292

How it was ported

release/2.0's release.yml was byte-identical to pre-fix main, so main's finished workflow was
applied wholesale; the pyproject/test/conftest edits were re-applied (their blocks were identical to
main's). CHANGELOG gets an [Unreleased] entry (the JAR fix is user-facing here).

Verification

Built on this branch (with .git, the CI condition):

uv build
# cldk-2.0.0rc1-py3-none-any.whl = 32,428,510 B -> cldk/analysis/java/codeanalyzer/jar/codeanalyzer-2.4.1.jar
# cldk-2.0.0rc1.tar.gz = 32,435,956 B -> (JAR present)

tests/analysis/java/test_jcodeanalyzer.py → 42 passed. No 2.0 release cut here — this only updates the branch.