feat(deps): add fish-deps unified dependency management command

Introduces `fish-deps` with four subcommands:
- status: colored installed/missing report per tier (required/integrations/recommended)
- install: interactively install each missing dep, prompts method when multiple exist
- update: update all installed deps using their preferred method
- sync: install missing then update installed

Install method priority: cargo (Rust tools get latest crate) > system PM
(paru/pacman/apt/brew/pkg/dnf/yum) > git clone (fzf via fzf-update) >
curl installer (starship, fisher) > pipx (wakatime).

Splits into focused helper files:
- _fish_deps_catalog.fish: parallel-array dep catalog with tiers, cargo crates, PM names, special install keys
- _fish_deps_pm.fish: PM detection and install/upgrade helpers
- _fish_deps_status.fish: tier-grouped colored status display
- _fish_deps_install.fish: per-dep interactive install with method selection
- _fish_deps_update.fish: per-dep update using known install method

check_fish_deps becomes a thin wrapper delegating to `fish-deps status`.
README updated with Dependency Management section.

functions/_fish_deps_catalog.fish

@@ -0,0 +1,52 @@
+# Copyright (C) 2026 Rootiest
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+# Populates parallel arrays describing every managed dependency.
+# Callers must invoke this function before accessing _fdc_* variables.
+#
+# 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 |
+#                  paru-build | pipx | curl-installer | "" (none)
+function _fish_deps_catalog
+    set -g _fdc_bins \
+        fish 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 req \
+        int int \
+        rec rec rec rec rec rec rec rec rec rec rec rec rec rec
+
+    set -g _fdc_cargo \
+        "" "" starship "" zoxide "" "" \
+        "" "" \
+        eza lsd bat "" du-dust "" "" "" ripgrep "" "" trash-cli "" ""
+
+    set -g _fdc_pm \
+        fish "" starship fzf zoxide direnv paru \
+        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 \
+        pipx "" \
+        "" "" "" "" "" "" "" "" "" "" "" "" "" ""
+end
+
+# Returns the index (1-based) of $argv[1] in the catalog, or "" if not found.
+function _fish_deps_catalog_idx --argument-names bin
+    _fish_deps_catalog
+    set -l i 1
+    for b in $_fdc_bins
+        if test "$b" = "$bin"
+            echo $i
+            return
+        end
+        set i (math $i + 1)
+    end
+end