refactor(ase): consume external abacuslite plugin

[QuantumMisaka]

Reminder

• I have read AGENTS.md and docs/developers_guide/agent_governance.md.
• I have linked an issue or explained why this PR does not need one.
• I have added adequate unit tests and/or case tests, or explained why not.
• I have listed the exact verification commands run and their results.
• I have described user-visible behavior changes, including INPUT parameter changes.
• I have explained core-module impact for ESolver, HSolver, ElecState, Hamilt, Operator, Psi, or other source/ changes.
• If this changes interfaces/ASE_interface/, source/source_relax/socket_*, or the socket metadata schema, I linked the abacuslite counterpart and updated the compatibility contract.
• I have requested any needed governance exception below.

Linked Issue

Fix #8165. This PR implements the fully external direction agreed in that issue. LTS workflow adoption will be tracked in a separate follow-up.

ABACUS-side counterpart: QuantumMisaka/abacuslite#5.

Unit Tests and/or Case Tests for my changes

• Commands run:
  • cd interfaces/ASE_interface/tests && conda run -n atst-dev python -m unittest test_external_provenance test_harness_facts test_native_md_fixture test_portable_runner -v
  • conda run -n atst-dev python -m py_compile interfaces/ASE_interface/tests/*.py
  • conda run -n atst-dev python -c "import yaml; yaml.safe_load(open('.github/workflows/ase_plugin_test.yml'))"
  • git diff --check
• Result summary: 16 offline harness tests passed, including the new failed-leader process-group regression under installed abacuslite 1.1.0; Python compilation, workflow YAML parsing and diff checks passed. The new SocketDriverTest.PropertiesMetadataDeclaresVersionedSchema covers the v1 schema string.
• Docs link fix: the first Read the Docs build failed because MyST treated the out-of-tree interfaces/ASE_interface/README.md relative link as a Sphinx cross-reference. The link now targets the GitHub tree, and no relative .md target remains in ase.md.
• Checks not run locally, with reason: no local ABACUS executable/build was available, so CTest and the nine real-engine cases were not run locally. The hosted Atomic Simulation Environment (ASE) Interface Test / abacuslite external job passed on run 39146599381, including SCF, ASE relax/MD, native MD, band, magnetic and socket checks. Both Read the Docs builds also passed after the link fix.

What's changed?

• Remove the vendored interfaces/ASE_interface/abacuslite package, its pyproject.toml, examples and internal developer guide. The plugin is now fully external; it is neither vendored nor a git submodule, so source archives remain complete.
• Keep interfaces/ASE_interface/tests as the engine-owned compatibility harness. It imports the installed abacuslite distribution, verifies provenance and wheel/runtime identity, and runs SCF, ASE relax/MD, native MD, band, magnetic and socket checks.
• Make the ASE CI workflow external-only: it installs the published abacuslite==1.1.0 wheel (SHA256 pinned) or a reviewed candidate ref, builds ABACUS, and runs every required case. A weekly schedule supplements PR checks.
• Document abacus.socket.properties.v1 comprehensively: additive fields stay in v1; a breaking change needs a new schema version and a transition in both ABACUS and abacuslite. Add kPropertiesSchema and an engine-side contract test.
• Add a PR-template reminder to link the abacuslite counterpart for ASE/socket changes.
• Point user installation and examples to the abacuslite package/repository.

Governance Notes

• INPUT/docs changes: docs/advanced/interface/ase.md, interfaces/ASE_interface/README.md and interfaces/README updated. No INPUT parameter metadata or generated documentation changes.
• Core module impact: source/source_relax/socket_utils.{h,cpp} only moves the existing schema literal into kPropertiesSchema; wire values and numerical behavior are unchanged. No ESolver, HSolver, ElecState, Hamilt, Operator or Psi changes.
• Exceptions requested: none.

[ABACUS-PR-BOT]

Static review of 6b37c6b1c5e168540540f11f80974298cc64ff42. Two nonblocking follow-ups below. No builds or runtime tests were run, and CI was not independently verified.