Release v0.4.0

[bburda]

Pull Request

Summary

Release v0.4.0 - version bumps across all 13 packages, comprehensive documentation overhaul, and release tooling.

Version bumps:

• All 13 package.xml files bumped from 0.3.0 to 0.4.0
• version.hpp fallback updated
• docs/conf.py version updated

Documentation overhaul:

• Root README rewritten with narrative style, entity tree examples, accurate feature table
• 6 new package READMEs (cmake, linux_introspection, beacon_common, param_beacon, topic_beacon, graph_provider)
• Gateway README updated with scripts, OpenAPI, vendor extension, locking endpoints
• 4 new Sphinx tutorials (locking, scripts, beacon discovery, OpenAPI/Swagger)
• Plugin system tutorial updated with ScriptProvider and PluginContext v4
• Scripts + Authentication config sections added to server.rst
• rest.rst version fixes and locking cross-reference
• Roadmap updated with milestone completion markers
• changelog.rst rewritten to aggregate all 13 package changelogs via include directives
• 7 new design docs with symlinks and toctree entries
• Gateway changelog fixed: moved post-0.3.0 items (docs+fix: update documentation and API responses for post-0.3.0 changes #258, feat: Linux introspection plugins (procfs, systemd, container) #263) from 0.3.0 section to 0.4.0

Release tooling:

• New scripts/release.sh for automated version bump and verification

Review fixes:

• Fixed hardcoded "0.3.0" in test_capability_generator.cpp (use kGatewayVersion)
• Fixed beacon README parameter names to match source code
• Fixed OpenAPI version string (3.0 -> 3.1.0) in README and CHANGELOG
• Added security warnings to auth config examples
• Fixed pip -> pipx in Contributing section

---

Issue

• closes Release v0.4.0 #278

---

Type

• Bug fix
• New feature or tests
• Breaking change
• Documentation only

---

Testing

• Sphinx build passes with -W (warnings as errors)
• Pre-commit hooks pass on all files
• ./scripts/release.sh verify 0.4.0 confirms all 13 packages + version.hpp are consistent
• test_capability_generator.cpp uses version-agnostic assertion

---

Checklist

• Breaking changes are clearly described (and announced in docs / changelog if needed)
• Tests were added or updated if needed
• Docs were updated if behavior or public API changed

[mfaferek93]

Minor: Script bumps all package.xml + version.hpp but not docs/conf.py (which was manually bumped in this PR). Next release will forget. Consider adding:

CONF_PY="${REPO_ROOT}/docs/conf.py"
if [ -f "$CONF_PY" ]; then
    sed -i "s|^version = \".*\"|version = \"${target_version}\"|" "$CONF_PY"
    sed -i "s|^release = \".*\"|release = \"${target_version}\"|" "$CONF_PY"
fi

Same for verify - check conf.py version too.