chezmoi v2: omz + p10k + fzf + vi-mode zsh, tmux, per-account gitconfig (#612)

Rewrote the Aug-1 sandbox-era source into a full workstation setup for
both ultix-streaming accounts: oh-my-zsh with autosuggestions/
syntax-highlighting/completions + powerlevel10k (pinned externals),
fzf wiring, vi mode, tmux conf, aliases under ~/.config/zsh, gitconfig
template that keeps hooksPath/tea for reachableceo only.

Detail + verification: https://projects.knownelement.com/issues/612#note-3335

.chezmoiexternal.toml

@@ -0,0 +1,37 @@
+# oh-my-zsh + custom plugins/themes, fetched at apply time.
+# Tag archives = pinned; branch archives re-check per refreshPeriod.
+# NOTE: no "exact" on .oh-my-zsh so custom/ additions survive refresh.
+
+[".oh-my-zsh"]
+    type = "archive"
+    url = "https://github.com/ohmyzsh/ohmyzsh/archive/refs/heads/master.tar.gz"
+    stripComponents = 1
+    refreshPeriod = "720h"
+
+[".oh-my-zsh/custom/plugins/zsh-autosuggestions"]
+    type = "archive"
+    url = "https://github.com/zsh-users/zsh-autosuggestions/archive/refs/tags/v0.7.1.tar.gz"
+    stripComponents = 1
+    exact = true
+    refreshPeriod = "720h"
+
+[".oh-my-zsh/custom/plugins/zsh-syntax-highlighting"]
+    type = "archive"
+    url = "https://github.com/zsh-users/zsh-syntax-highlighting/archive/refs/heads/master.tar.gz"
+    stripComponents = 1
+    exact = true
+    refreshPeriod = "720h"
+
+[".oh-my-zsh/custom/plugins/zsh-completions"]
+    type = "archive"
+    url = "https://github.com/zsh-users/zsh-completions/archive/refs/heads/master.tar.gz"
+    stripComponents = 1
+    exact = true
+    refreshPeriod = "720h"
+
+[".oh-my-zsh/custom/themes/powerlevel10k"]
+    type = "archive"
+    url = "https://github.com/romkatv/powerlevel10k/archive/refs/heads/master.tar.gz"
+    stripComponents = 1
+    exact = true
+    refreshPeriod = "720h"