fix(deps): demote uv to recommended, remove dead pipx installer code

uv is only used in the fish-deps fish-from-source build path
(uv run --no-managed-python cargo install --path .) and is not required
by the config at runtime. All consumers degrade gracefully without it.

pipx appeared in the installer's method-building and execution switch
blocks but no catalog entry ever sets special=pipx, making both branches
permanently unreachable dead code. The docs listed pipx as install
priority #6 which was equally misleading.

- _fish_deps_catalog: change uv tier from req → rec
- _fish_deps_install: remove case pipx method-builder and
  special-pipx / special-pip execution cases
- docs/fish-config.md: move uv from Required to Recommended catalog
  entry with accurate description; drop pipx from install priority
  list and tier summary

functions/_fish_deps_catalog.fish

@@ -19,7 +19,7 @@ function _fish_deps_catalog
         eza lsd bat btop dust duf prettyping ov rg lazygit lazydocker trash kitty wezterm python3
 
     set -g _fdc_tiers \
-        req req req req req req req req rec rec \
+        rec req req req req req req req rec rec \
         int int \
         rec rec rec rec rec rec rec rec rec rec rec rec rec rec rec
 

functions/_fish_deps_install.fish

@@ -117,14 +117,6 @@ function _fish_deps_install
                         set -a methods special-yay
                         set -a method_labels "build from AUR (makepkg)"
                     end
-                case pipx
-                    if type -q pipx
-                        set -a methods special-pipx
-                        set -a method_labels "pipx ($bin)"
-                    else if type -q pip
-                        set -a methods special-pip
-                        set -a method_labels "pip install --user ($bin)"
-                    end
             end
 
             if test (count $methods) -eq 0
@@ -264,10 +256,6 @@ function _fish_deps_install
                     popd 2>/dev/null
                     rm -rf "$_tmpdir"
                     test $_build_ok -eq 1
-                case special-pipx
-                    pipx install $bin
-                case special-pip
-                    pip install --user $bin
             end
 
             if test $status -eq 0