feat: surface repo root in runtime prompt

docs/gateway/configuration.md

@@ -1266,6 +1266,18 @@ Default: `~/clawd`.
 If `agents.defaults.sandbox` is enabled, non-main sessions can override this with their
 own per-scope workspaces under `agents.defaults.sandbox.workspaceRoot`.
 
+### `agents.defaults.repoRoot`
+
+Optional repository root to show in the system prompt’s Runtime line. If unset, Clawdbot
+tries to detect a `.git` directory by walking upward from the workspace (and current
+working directory). The path must exist to be used.
+
+```json5
+{
+  agents: { defaults: { repoRoot: "~/Projects/clawdbot" } }
+}
+```
+
 ### `agents.defaults.skipBootstrap`
 
 Disables automatic creation of the workspace bootstrap files (`AGENTS.md`, `SOUL.md`, `TOOLS.md`, `IDENTITY.md`, `USER.md`, and `BOOTSTRAP.md`).