M0: scaffold Cargo workspace, core types, event bus, permission engine, storage actor

Seven-crate workspace per docs/01-architecture.md. harness-core gets the
domain types (Session/Message/Part/ToolState), a broadcast EventBus, the
last-match-wins wildcard permission evaluator, and a SQLite storage actor
(dedicated thread + mpsc, JSON-blob rows) with roundtrip tests. All other
crates are compiling stubs. CI runs fmt/clippy -D warnings/test.

crates/harness-core/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "harness-core"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+tokio = { workspace = true }
+tokio-util = { workspace = true }
+futures = { workspace = true }
+async-trait = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
+schemars = { workspace = true }
+rusqlite = { workspace = true }
+globset = { workspace = true }
+ulid = { workspace = true }
+thiserror = { workspace = true }
+tracing = { workspace = true }
+
+[dev-dependencies]
+tokio = { workspace = true, features = ["test-util", "macros"] }
+
+[lints]
+workspace = true