Use pyicu-wheels for tests via PEP 735 dependency groups; remove redundant optional-deps

[Copilot]

Installing pyicu for testing required compiling ICU from source on macOS (via Homebrew) and downloading unofficial wheels on Windows. Development/testing deps were also mixed into [project.optional-dependencies], which is meant for end-users.

What do these changes do

• Introduces PEP 735 [dependency-groups] in pyproject.toml covering all test suites (test-core, test-compact, test-extra, test-noauto-{torch,tensorflow,onnx,cython,network}, test-corpus, test-full) plus dev and docs
• Replaces pyicu with pyicu-wheels in all test groups — pre-built wheels for all platforms, no compilation needed
• Removes compact, extra, noauto-*, full, dev, docs from [project.optional-dependencies]; feature sets (icu, spell, wordnet, etc.) remain untouched
• Updates all CI workflows to use pip install --group <name>
• Removes macOS brew install icu4c and Windows unofficial-wheel-download steps from unittest.yml

# Before
pip install ".[compact]"         # required compiling ICU on macOS/Windows

# After
pip install pythainlp
pip install --group test-compact  # resolves pyicu-wheels pre-built wheel

What was wrong

[project.optional-dependencies] grouped both end-user feature sets and test/dev tooling together. Testing with pyicu required platform-specific ICU compilation or unofficial binary sources, making local setup on macOS/Windows unnecessarily difficult.

How this fixes it

PEP 735 [dependency-groups] cleanly separates dev/test deps from the distributed package metadata. Substituting pyicu-wheels (Init7's pre-built distribution, for testing only — distribution deps still declare pyicu) eliminates all platform-specific ICU setup steps in CI and locally.

Security note: pyicu-wheels is a third-party pre-built distribution of PyICU by Init7, scoped to test groups only. The published package's icu = ["pyicu>=2.3"] optional-dep continues to reference the official PyICU package.

Your checklist for this pull request

• Passed code styles and structures
• Passed code linting checks and unit test

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Use pyicu-wheels for tests</issue_title>
<issue_description>Consider to use https://pypi.org/project/pyicu-wheels/ (source code https://github.com/Init7/pyicu) instead of https://pypi.org/project/pyicu/ (source code https://gitlab.pyicu.org/main/pyicu), for testing purpose.

• This will allow easier test on Windows / macOS locally (currently, it is quite complicated to install pyicu on macOS as it involves compiling and link with icu4c / for Windows user, it require a download from separated source)
• Maybe quicker in CI as it doesn't require build the lib from scratch

For distribution, the declared project dependency in pyproject.toml should still stick to https://pypi.org/project/pyicu/.

Each test suite dependencies could be declared by using the PEP 735 dependency groups https://packaging.python.org/en/latest/specifications/dependency-groups/#dependency-groups. Modify pyproject.toml for that. Modify test workflow accordingly (for example, use pip install --group)

Make sure that dependency groups for test suites are covering what are actually needed by the test suites (core, compact, extra, noauto, corpus) See https://github.com/PyThaiNLP/pythainlp/blob/dev/tests/README.md

The main goal is to allow developers to install pythainlp dependency for testing purpose easily -- without the need to compile pyicu themselves.

The second goal is, once the first goal is achieved, it will simplify the CI in .github/workflows/unittest.yml
</issue_description>

<agent_instructions>As https://github.com/Init7/pyicu is not the official repo of PyICU, be mindful about possible security issues.</agent_instructions>

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

• Fixes Use pyicu-wheels for tests #1336

---

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[coveralls]

coverage: 66.312%. remained the same
when pulling d8a1e3b on copilot/use-pyicu-wheels-for-tests
into fcb9210 on dev.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[bact]

pyicu-wheels does not provide a wheel for Python 3.9 on Windows.
May need to stick with current setup for a while.

But Python 3.9 is EOL and PyThaiNLP 6.0.0 may move to Python 3.10, so it is possible to proceed at that point.

Keep this PR open.