feat(tools): add run_shell, edit_file, write_file + read_file directory listing

Four standard-tier tool extensions (one tool per extension, zero ABI change):
- tool-read-file: read_file now lists directory contents (sorted, /-suffixed subdirs)
- tool-shell: run_shell (foreground, streamed, cancellable, cwd, timeout + output cap)
- tool-edit-file: edit_file (oldString/newString/replaceAll; errors on absent/non-unique)
- tool-write-file: write_file (explicit overwrite flag)
Registered in host-bin CORE_EXTENSIONS. Live boot clean (shell capability accepted).
686 vitest + 89 bun = 775 tests; tsc -b EXIT 0; biome clean.

1 files changed, 3 insertions, 0 deletions

diff --git a/packages/tool-shell/src/index.ts b/packages/tool-shell/src/index.ts
new file mode 100644
index 0000000..efd36fc
--- /dev/null
+++ b/packages/tool-shell/src/index.ts
@@ -0,0 +1,3 @@
+export { extension } from "./extension.js";
+export type { SpawnResult, SpawnShell, ValidatedArgs } from "./shell.js";
+export { createRunShellTool } from "./shell.js";