feat(deps): add cargo as a managed dependency with rustup installer

cargo is now the second entry in the catalog (after fish) so it is
installed before any Rust tool that depends on it. Install preference:
rustup installer (curl | sh) first, system PM as fallback. Update
runs rustup update when rustup is available.

The rustup-installer special is evaluated before the system PM in the
method list so it is always option 1 / the default for cargo.

functions/_fish_deps_catalog.fish

@@ -2,38 +2,40 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
 # Populates parallel arrays describing every managed dependency.
-# Callers must invoke this function before accessing _fdc_* variables.
+# Callers must invoke this function before accessing _fdc_* arrays.
 #
 # Array layout (same index across all sets):
 #   _fdc_bins    — binary name (what `type -q` checks)
 #   _fdc_tiers   — req | int | rec
 #   _fdc_cargo   — cargo crate name, or "" if not on crates.io
 #   _fdc_pm      — system PM package name, or "" if not in repos
-#   _fdc_special — special install key: fisher-bootstrap | fzf-update |
-#                  pipx | curl-installer | "" (none)
+#   _fdc_special — special install key: rustup-installer | fisher-bootstrap |
+#                  fzf-update | paru-build | pipx | curl-installer | "" (none)
+#
+# cargo is listed second so it is installed before Rust tools that depend on it.
 function _fish_deps_catalog
     set -g _fdc_bins \
-        fish fisher starship fzf zoxide direnv paru \
+        fish cargo fisher starship fzf zoxide direnv paru \
         wakatime tailscale \
         eza lsd bat btop dust duf prettyping most rg lazygit lazydocker trash kitty wezterm
 
     set -g _fdc_tiers \
-        req req req req req req rec \
+        req req req req req req req rec \
         int int \
         rec rec rec rec rec rec rec rec rec rec rec rec rec rec
 
     set -g _fdc_cargo \
-        "" "" starship "" zoxide "" "" \
+        "" "" "" starship "" zoxide "" "" \
         "" "" \
         eza lsd bat "" du-dust "" "" "" ripgrep "" "" trash-cli "" ""
 
     set -g _fdc_pm \
-        fish "" starship fzf zoxide direnv "" \
+        fish cargo "" starship fzf zoxide direnv "" \
         wakatime tailscale \
         eza lsd bat btop dust duf prettyping most ripgrep lazygit lazydocker trash kitty wezterm
 
     set -g _fdc_special \
-        "" fisher-bootstrap curl-installer fzf-update "" "" paru-build \
+        "" rustup-installer fisher-bootstrap curl-installer fzf-update "" "" paru-build \
         pipx "" \
         "" "" "" "" "" "" "" "" "" "" "" "" "" ""
 end