shell: starship + shared aliases for bash and zsh

- .chezmoidata/aliases.yaml: single source for shell-agnostic aliases
- fish 20-aliases.fish -> .tmpl rendered from that data (fish-only
  bits: clipboard detection, q function, interactive eza)
- dot_config/shell/aliases.sh.tmpl: same data for bash/zsh
- dot_bashrc/dot_zshrc: managed rc files with starship init
  (replaces unmanaged flyline/p10k prompts), guarded cargo/atuin/envman

README.md

@@ -28,11 +28,15 @@ layer (niri, noctalia, fontconfig, systemd user units) — `mac` and
 
 ## What's managed
 
-Universal: fish, nvim (AstroNvim), tmux, kitty, yazi, lazygit,
-lazydocker, gh (+ extensions), starship, git, ssh config, Claude Code
-(settings/commands/hooks/skills). Packages declared in
-`.chezmoidata/packages.yaml`, installed by `.chezmoiscripts` (idempotent,
-re-run when the manifest changes).
+Universal: fish, bash + zsh (starship prompt, shared aliases), nvim
+(AstroNvim), tmux, kitty, yazi, lazygit, lazydocker, gh (+ extensions),
+starship, git, ssh config, Claude Code (settings/commands/hooks/skills).
+Packages declared in `.chezmoidata/packages.yaml`, installed by
+`.chezmoiscripts` (idempotent, re-run when the manifest changes).
+
+Aliases are defined once in `.chezmoidata/aliases.yaml` and rendered
+into fish (`fish/conf.d/20-aliases.fish`) and bash/zsh
+(`~/.config/shell/aliases.sh`, sourced by `.bashrc`/`.zshrc`).
 
 Linux desktop (role `desktop`/`laptop` only): niri, noctalia,
 fontconfig, mimeapps, systemd user units, niri-launch.