feat(skills): add native xint / xint-rs content intelligence skill

[0xNyk]

Summary

• add new built-in xint skill at skills/content/xint/SKILL.md
• add skills/content/DESCRIPTION.md
• add native xint tool integration (tools/xint_tool.py) for executing xint-rs (preferred) or xint (fallback)
• wire native tool into discovery + toolsets:
  • model_tools.py discovery import
  • toolsets.py new xint toolset + include in Hermes core tools
  • tools/__init__.py exports
• add unit tests for native tool behavior (tests/tools/test_xint_tool.py)

Why

This ships both:

1. a reusable skill guide for X intelligence workflows, and
2. an actual callable native tool so the agent can run xint/xint-rs directly.

Validation

• ✅ source .venv/bin/activate && python -m pytest tests/tools/test_xint_tool.py tests/test_toolsets.py tests/test_model_tools.py -q (40 passed)
• ✅ source .venv/bin/activate && python -m pytest tests/agent/test_prompt_builder.py -q (33 passed)
• ⚠️ source .venv/bin/activate && python -m pytest tests/ -q still has a pre-existing unrelated failure in this environment:
  • tests/test_timezone.py::TestCronTimezone::test_get_due_jobs_handles_naive_timestamps

Notes

• native tool is availability-gated: it only appears when xint-rs or xint is in PATH
• command execution is argument-list based (no shell interpolation)
• outputs are structured JSON with exit code/stdout/stderr (+ optional stdout JSON parsing)

[0xNyk]

Update after branch cleanup/rebase:

• Removed unintended cron/jobs.py change from this PR (scope is now xint-only).
• Rebased on current main; PR is mergeable.
• CI is green on this branch (test workflow passed).

Validation run locally:

• python -m pytest -o addopts='' tests/tools/test_xint_tool.py tests/test_toolsets.py tests/test_model_tools.py tests/agent/test_prompt_builder.py -q -> 94 passed
• Runtime smoke check via wrapper:
  • call: tools.xint_tool.xint_tool(action='--help', prefer='auto')
  • resolved executable: /opt/homebrew/bin/xint
  • exit code: 0

Integration included in this PR:

• Native tool: tools/xint_tool.py
• Discovery/toolset wiring: model_tools.py, toolsets.py, tools/__init__.py
• Skill docs: skills/content/xint/SKILL.md, skills/content/DESCRIPTION.md
• Tests: tests/tools/test_xint_tool.py

Happy to add any additional validation maintainers want.

[0xNyk]

Quick maintainer ping for review 🙏\n\nThis PR has been scope-cleaned to xint integration only, rebased on latest main, and CI is green (test workflow passing).\n\nIncluded in this PR:\n- native xint tool wiring (registry + toolsets + discovery)\n- xint skill/docs updates\n- test coverage for tool behavior\n\nIf the approach looks good, this should be ready to merge.