Consume generated agent guidance from the canonical Docs source

[konojunya]

Summary

• Pin the merged Docs source revision and manifest digest.
• Replace hand-maintained skill instructions with the verified generated artifact.
• Add explicit sync and read-only drift checks with immutable URL, schema, and integrity validation.
• Keep the existing skill installation entry point and process-level CLI test.

Validation

• Three consumer and negative tests passed.
• Live pinned Docs retrieval, sync, and byte comparison passed.
• Generated skill commands passed the CLI process integration test.
• Rust formatting and whitespace checks passed.