zsh: adopt deja predictive autosuggestions; make deja install version-aware

- .zshrc: replace the zsh-autosuggestions plugin with deja (deja supersedes
  it), and move the auto-dedup PATH block to the top so ~/.local/bin is on
  PATH before plugins/modules load.
- bootstrap scripts (arch/debian + gentoo): clone the deja OMZ plugin and
  install the deja binary via the official checksum-verified installer. The
  binary install now compares the installed version to the latest release
  tag and re-runs the installer when they differ, so re-running the script
  UPGRADES deja (0.4.1 -> 0.4.2) rather than skipping an existing install.

dot_zshrc.tmpl

@@ -4,6 +4,19 @@
 #  Sync source: https://git.melonbread.xyz/rain/gnu-plus-dotfiles
 # =============================================================================
 
+# ---------------------------------------------------------------------------
+# PATH (auto-deduplicated)
+# ---------------------------------------------------------------------------
+typeset -U path
+path=(
+    {{- if not (not (stat "/opt/rocm/bin")) }}
+    /opt/rocm/bin                      # ROCm tools first (rocminfo, rocm-smi, amd-smi, hipcc, etc.)
+    {{- end }}
+    $HOME/.local/bin
+    $HOME/.bin
+    $path
+)
+
 # ---------------------------------------------------------------------------
 # Oh My Zsh
 # ---------------------------------------------------------------------------
@@ -25,7 +38,7 @@ plugins=(
     fzf-tab                       # navigable Tab completion menu
     zsh-syntax-highlighting       # fish-style live colors — MUST be near last
     zsh-history-substring-search  # fish-style Up/Down history search
-    zsh-autosuggestions           # fish-style ghost completions — MUST be last
+    deja                          # predictive ghost completions — MUST be last (replaces zsh-autosuggestions)
 )
 
 
@@ -85,18 +98,6 @@ export TMUX_PLUGIN_MANAGER_PATH=~/.tmux/plugins/tpm
 # Debian: ROCm only relevant if you install it. Leave default until needed.
 {{ end -}}
 
-# ---------------------------------------------------------------------------
-# PATH (auto-deduplicated)
-# ---------------------------------------------------------------------------
-typeset -U path
-path=(
-    {{- if not (not (stat "/opt/rocm/bin")) }}
-    /opt/rocm/bin                      # ROCm tools first (rocminfo, rocm-smi, amd-smi, hipcc, etc.)
-    {{- end }}
-    $HOME/.local/bin
-    $HOME/.bin
-    $path
-)
 
 # ---------------------------------------------------------------------------
 # Aliases — common + OS-specific