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

Sets up the Cargo workspace (harness-core, harness-tools, harness-providers, harness-mcp, harness-lsp, harness-app, harness-tui) and the ten architecture docs under docs/. harness-core gets its foundational types (session/message/part/model ids), an in-process event bus, a table-driven permission evaluate function, and a SQLite-backed storage actor with schema and roundtrip coverage. Every crate compiles empty and a bin stub prints its version.

crates/harness-app/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "harness-app"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+harness-core = { workspace = true }
+harness-providers = { workspace = true }
+harness-tools = { workspace = true }
+harness-mcp = { workspace = true }
+harness-lsp = { workspace = true }
+
+[lints]
+workspace = true

crates/harness-app/src/lib.rs

@@ -0,0 +1 @@
+// Composition root: builds the Engine and registers providers/tools/mcp/lsp. Lands in M1+.