Release v0.8.0

[0.8.0] - 2026-05-02

• Added describe_diff tool: analyze staged and unstaged git changes with an LLM to produce a release summary, release notes, commit message, and risk notes — without making any modifications.
• Release notes generated during the release workflow are now LLM-written from actual diff content instead of a plain list of changed filenames.
• Fixed AI Layer base URL resolution so the /api path suffix is always correctly appended regardless of how AI_LAYER_URL is configured.
• Introduced a dedicated rel-ease-diff-describer agent with its own configurable ID (REL_EASE_DIFF_AGENT_ID env var) for diff summarization, independent of the version-bump agent.