chore: Update developer environment tooling

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "lib-herdr"]
+	path = lib-herdr
+	url = https://github.com/herdrdev/herdr.git

README.md

@@ -14,6 +14,7 @@ machines.
   - [AI agent skills](#ai-agent-skills)
   - [Neovim Configuration](#neovim-configuration)
   - [Terminal Environment: tmux, zsh, bun](#terminal-environment-tmux-zsh-bun)
+  - [Herdr configuration](#herdr-configuration)
   - [Codex config](#codex-config)
   - [WSL Clipboard Integration](#wsl-clipboard-integration)
 - [Requirements](#requirements)
@@ -106,6 +107,28 @@ See the [Codex skills documentation](https://developers.openai.com/codex/concept
 - Bun JavaScript/TypeScript runtime integration
 - `tree-sitter-cli` support for Neovim parser installation on the `main` branch
 
+### Herdr configuration
+
+[`herdr/config.toml`](herdr/config.toml) is the managed configuration source.
+`symlinks.sh` links only this file to `~/.config/herdr/config.toml`; Herdr's
+sessions and logs remain runtime-owned and are never linked or versioned.
+Like the existing dotfiles links, sync replaces the runtime config with this
+managed source. Backup/preservation or force-mode policies are deferred.
+
+The checked-in file is the complete annotated baseline generated by Herdr
+0.8.0. Its options are commented except for upstream's explicit
+`pane_history = false` default, so it preserves built-in behavior until an
+option is deliberately changed. Refresh it only when deliberately adopting a
+new Herdr baseline:
+
+```bash
+herdr --default-config
+```
+
+The upstream source is available as the pinned `lib-herdr` submodule for local
+documentation and implementation inspection. Initialize it after cloning
+dotfiles with `git submodule update --init --recursive`.
+
 ### Codex config
 
 [`codex/config.ts`](codex/config.ts) maintains portable defaults in

codex/config.test.ts

@@ -119,9 +119,9 @@ describe("codex config", () => {
       await writeFile(
         runtimePath,
         '[projects."/tmp/project"]\ntrust_level = "trusted"\n\n' +
-          "[mcp_servers.private]\ncommand = \"private-command\"\n\n" +
+          '[mcp_servers.private]\ncommand = "private-command"\n\n' +
           "[tui]\nvim_mode_default = false\n\n" +
-          "[tui.model_availability_nux]\n\"gpt-5.6-sol\" = 4\n",
+          '[tui.model_availability_nux]\n"gpt-5.6-sol" = 4\n',
       )
 
       await applyConfig({ runtimePath, mcpSourcePath, quiet: true })

herdr/README.md

@@ -0,0 +1,17 @@
+# Herdr configuration
+
+`config.toml` is the managed Herdr configuration. The dotfiles link script
+places it at `~/.config/herdr/config.toml`; Herdr session state and logs remain
+outside this directory.
+
+## Apply a configuration change
+
+Validate the managed configuration, then reload the running Herdr server:
+
+```bash
+HERDR_CONFIG_PATH="$DOTFILES/herdr/config.toml" herdr config check
+herdr server reload-config
+```
+
+The configuration key `keys.detach` uses `prefix+d`, matching tmux. This
+reserves `prefix+q` for the future pane picker.