refactor(pipeline): 移除空的 zclaw-kernel 依赖 (Phase 2A)

Pipeline 代码中无任何 zclaw_kernel 引用，依赖声明是遗留物。
移除后编译验证通过: cargo check --workspace --exclude zclaw-saas ✓

crates/zclaw-pipeline/Cargo.toml

@@ -25,7 +25,6 @@ reqwest = { workspace = true }
 # Internal crates
 zclaw-types = { workspace = true }
 zclaw-runtime = { workspace = true }
-zclaw-kernel = { workspace = true }
 zclaw-skills = { workspace = true }
 zclaw-hands = { workspace = true }