chore: Update developer environment tooling

[Unique-Divine]

Developer environment updates

This branch adds a managed Herdr configuration baseline, makes tmux agent
activity visible in window labels, and includes small Windows, shell, and test
maintenance updates for the personal development environment.

Rationale

Herdr needed a reproducible configuration source without versioning its live
session state or logs. The configuration remains close to upstream defaults so
future preferences can be introduced deliberately, while prefix+d preserves
the existing tmux detach muscle memory and leaves prefix+q available for pane
selection.

The tmux watcher already exposes agent activity through a user option, but the
status format did not render it. The branch also aligns Dracula's transparent
powerline cells with the transparent status bar.

Managed terminal configuration

dotfiles/herdr/config.toml  -> ~/.config/herdr/config.toml
Herdr sessions and logs     -> runtime-owned under ~/.config/herdr
prefix+d                    -> detach
prefix+q                    -> reserved for pane selection

The pinned lib-herdr submodule provides local source and documentation for
the configured Herdr version. The README documents config reload and source
initialization workflows.

Tmux agent presentation

tmux server starts
  -> optional tmux-agent-watch process starts once per server
  -> watcher updates @agent_watch_summary
  -> tmux window labels render the summary

The watcher launch remains conditional on the local binary, so tmux continues
to work normally when it is absent.

Key Changes

1. Add the Herdr source submodule, annotated default configuration, runtime
   config link, health check, and reload documentation.
2. Move Herdr detach to prefix+d and reserve prefix+q for the pane picker.
3. Render tmux agent-watch activity in window labels and fix transparent
   Dracula powerline corner backgrounds.
4. Add a WSL wrapper for restoring the classic Windows Explorer context menu.
5. Include sqlite3 in the baseline package list and apply small test-source
   style cleanups.