feat(deps): add Optional/Terminal Emulator tiers, fix docker prompt hang and ov install path

Reworks fish-deps' dependency classification from three tiers to five:
Required, Recommended, Optional, Terminal Emulators, and Integrations.

- Add an Optional tier for single-purpose wrapper conveniences that only
  matter if you already use that specific tool (btop, dust, duf,
  prettyping, go, lazygit, lazydocker, docker, yt-dlp, screen). Skipped by
  `fish-deps install`/`sync` by default.
- Split kitty/wezterm into their own Terminal Emulators tier, since only
  the one matching $TERM is ever relevant to a given user.
- Add --optional, --terminals, and --all flags to `install`/`sync` to
  opt back into the skipped tiers, with a summary of how many were
  skipped and which flag restores them.
- Fix `_fish_deps_status` marking missing Integrations as critical (red)
  the same as Required — only Required is red now; Recommended stays
  yellow, everything else renders as a neutral dim note.

Also fixes two bugs surfaced during dependency testing on a fresh
install:

- `fish_right_prompt` called `docker context show` on every prompt with
  no `type -q docker` guard, unlike every other optional integration in
  this config — on a system without docker this printed a visible
  "Unknown command: docker" block on every single prompt render. Added
  the missing guard, and hardened the `ld` wrapper with explicit
  docker/lazydocker presence checks.
- `ov`'s catalog entry offered `cargo install ov` as its preferred
  install method, but crates.io's `ov` is an unrelated crate, not the
  noborus/ov pager — cargo would silently install the wrong package.
  Removed the cargo path; `ov` now prefers `go install
  github.com/noborus/ov@latest` (ahead of the system PM) when go is
  available, since not all distros package `ov` in their base repos,
  and falls back to the system PM otherwise.

functions/fish_right_prompt.fish

@@ -9,10 +9,9 @@
 #
 # DESCRIPTION
 #   Renders the right-side prompt. Always shows a dim timestamp. When the last
-#   command failed, prefixes it with a red ✘ and the exit code. When starship
-#   is installed and C3 overrides are enabled, also shows the active Docker
-#   context (if non-default) — that block is paired with the starship prompt
-#   which already guards on both conditions.
+#   command failed, prefixes it with a red ✘ and the exit code. When docker
+#   and starship are both installed and C3 overrides are enabled, also shows
+#   the active Docker context (if non-default).
 #
 # EXIT STATUS
 #   0  Always
@@ -29,8 +28,10 @@ function fish_right_prompt
         set_color normal
     end
 
-    # Docker context — only relevant alongside the starship prompt
-    if type -q starship; and __fish_config_op_enabled __fish_config_op_overrides
+    # Docker context — only relevant alongside the starship prompt, and only
+    # when docker is actually installed (guarded like every other optional
+    # integration in this config).
+    if type -q docker; and type -q starship; and __fish_config_op_enabled __fish_config_op_overrides
         set -l docker_ctx (docker context show 2>/dev/null)
         if test -n "$docker_ctx"; and test "$docker_ctx" != default
             set_color blue