chore: public OSS release 2.9.3

[keshprad]

Summary

Publishes the public OSS snapshot for SkillSpector 2.9.3.

• Treat exhausted malformed structured LLM responses as non-fatal skipped work, keeping reports visibly degraded and incomplete.
• Preserve finding coverage for affected LLM analysis batches while other LLM failures remain fatal.
• Update version metadata, lockfile, changelog, release notes, and regression coverage.

Release provenance

• Internal source: main at 4c2b7585c88d13afb6028108944bbd5498379491
• Sanitized orphan branch: release/oss-2026-08-11 at c1661dbd59740614643338c8dbf2705ecbb2e53e
• Release notes: docs/release/skillspector-2.9.3.md

Public boundary

• No public-only workflows, templates, or policy files were modified or deleted.
• Removed one accidental trailing blank line from the exported Makefile before committing.

Validation

• make test-unit in the sanitized snapshot — 1943 passed, 13 skipped, 38 deselected, 4 xfailed.
• git diff --check origin/main — passed.
• Release CI — lint, unit, integration, Docker smoke, and Sonar passed.
• uv run --locked --extra dev python -m twine check on the release artifacts — passed.