M1: read, write, bash, glob, and grep tools

Implements the first five harness-tools: read, write, bash (with timeout/output truncation), glob, and grep, plus shared path-resolution helpers. Wires them into the core tool registry and processor.

crates/harness-tools/src/lib.rs

@@ -1 +1,25 @@
-// Built-in tools (bash, read, edit, write, glob, grep, todo, webfetch, task) land here in M1/M4.
+mod bash;
+mod glob;
+mod grep;
+mod paths;
+mod read;
+mod write;
+
+pub use bash::BashTool;
+pub use glob::GlobTool;
+pub use grep::GrepTool;
+pub use read::ReadTool;
+pub use write::WriteTool;
+
+use std::sync::Arc;
+
+use harness_core::tool::ToolRegistry;
+
+/// Registers the M1 built-ins (`edit` is added separately once its replacer chain lands).
+pub fn register_builtins(registry: &mut ToolRegistry) {
+    registry.register(Arc::new(ReadTool));
+    registry.register(Arc::new(WriteTool));
+    registry.register(Arc::new(BashTool));
+    registry.register(Arc::new(GlobTool));
+    registry.register(Arc::new(GrepTool));
+}