feat: align Herdr keyboard navigation with the desktop

Add direct Ctrl+Alt pane, workspace, picker and agent navigation while retaining prefix shortcuts. Manage the existing theme and sidebar preferences with the keymap in Home Manager. Record Herdr as the chosen manager and defer agent evaluation.

Formatting, rendered TOML parsing, flake evaluation, Zenith system build and whitespace checks passed. User activation and interactive keyboard acceptance remain; no live sessions were changed.

docs/constellation-work.md

@@ -83,10 +83,10 @@ coherent commit before starting unrelated work.
   in ordinary normal/visual buffers, and Blink Escape cancellation. The existing
   `tests/neovim-ergonomics.lua` is retained; earlier smoke-check evidence is in the
   archived plan, with interactive preview restoration/visual behavior unproven.
-- **Agents:** agent-deck, Herdr and tmux coexist; no replacement has been chosen.
+- **Agents:** Herdr is selected; agent-deck and tmux remain installed alongside it.
   Codex has agent-deck notifications and hooks enabled. Shared Context7/NixOS skills
   live under `.agents/skills`; a Nix-managed marketplace exposes Ponytail.
-  Zellij is also declared on workstations. None of this selects a session workflow.
+  Zellij is also declared on workstations. Detailed project workflow remains open.
 - **SharePoint:** Zenith declares an hourly service syncing `company-sharepoint:`
   into `~/.local/share/yookr-reference/sharepoint/Algemeen` and
   `company-sharepoint-projecten:` into `Projecten`. Each invocation has
@@ -122,10 +122,10 @@ The focus is the broader environment, not further API/database polish. Candidate
 areas remain places/ownership, navigation/interaction, human/agent collaboration,
 and system operation/maintenance; these are discussion areas, not a work queue.
 
-Current discussion: consistent project/agent work and Niri workspace use. The user
-values Herdr's spaces and overview of running/waiting agents, but dislikes its
-keybindings and mouse orientation. Agent-deck has startup issues (not diagnosed).
-Kitty/Niri, tmux and Zellij are candidates, not selected replacements.
+Current choice: keep Herdr and configure its keys. The user likes its structure,
+spaces and overview; keyboard interaction is the issue. Agent evaluation is
+explicitly deferred. Do not resume replacement-tool comparisons or ask for an
+evaluation task/budget as a prerequisite for this work.
 
 Read-only inspection found existing Niri overview, workspace movement and tabbed
 columns; Kitty has no declared project/session organization. Installed versions:
@@ -145,22 +145,33 @@ worktrees for independent writing efforts, one integration owner. Keep enduring
 repository rules in AGENTS.md, current goals/acceptance in task prompts, and durable
 decisions/current state in existing project docs. No fixed agent team is selected.
 
-Proposed comparison: hold the desktop and model settings fixed; compare solo,
-solo plus independent review, then bounded parallel delegation on the same starting
-commit and task. Record accepted correctness, unnecessary complexity, human
-interventions/rework, total completion time and aggregate usage including workers.
-Use fresh isolated runs and common acceptance checks; repeat promising variants
-before drawing reliability conclusions. Measure desktop navigation separately.
-[Codex subagents](https://learn.chatgpt.com/docs/agent-configuration/subagents)
-and [evaluation guidance](https://developers.openai.com/api/docs/guides/evaluation-best-practices)
-support bounded delegation and task-specific evaluation; the proposed trial is
-not a measured result. No benchmark framework or comparative runs created.
+Herdr configuration is now declared in `modules/capabilities/ai.nix`, including
+the existing Kanagawa theme, workspace-sorted agent panel and disabled toasts.
+Home Manager owns `~/.config/herdr/config.toml` after activation; maintain these
+preferences in Nix. Its configured `.bak` mechanism preserves the previous regular
+file. Direct Ctrl+Alt bindings supplement the existing Ctrl+B prefix shortcuts:
 
-Inputs requested together: typical project/agent count and clients; required
-persistence (project switch, terminal close, logout/reboot, remote connection);
-a representative trial task and rough time/spend limit. These determine the first
-concrete trial. No configuration changes, tests, activation or agent runs in this
-discussion; documentation whitespace checked.
+| Ctrl+Alt + | Action |
+| --- | --- |
+| H / J / K / L | Focus pane left / down / up / right |
+| U / I | Next / previous workspace |
+| O / G | Workspace picker / goto picker |
+| 1–9 | Focus agent |
+| [ / ] | Previous / next tab |
+| Enter | New tab |
+| V / Minus | Split right / down |
+| F | Zoom pane |
+| Q | Detach, leaving the session running |
+
+Inside workspace navigation, U/I moves down/up and H/J/K/L retains pane navigation.
+Niri and Kitty bindings are unchanged. Syntax and action names were checked against
+the installed Herdr 0.9.0 default config and current upstream documentation.
+Interactive delivery through Kitty remains for user acceptance after activation.
+Reload Herdr with its existing Ctrl+B then Shift+R binding after activating Nix.
+Verification: repository formatting, rendered TOML parsing, flake evaluation,
+Zenith no-link system build and whitespace checking passed. No tests, activation
+or live Herdr session changes performed. Next input is the user's activation and
+combined feedback on pane/workspace movement, the pickers and agent jumps.
 
 Mail search remains unresolved. The workbench's custom mail reader, inventory
 pilot, justfile and old README are archived; native Garden/kubectl/K9s now own the