Clean up zshrc: drop bashrc source, OMZ git plugin, conflicts

[akan72]

Summary

Branch 2 of the dotfiles cleanup (stacked on akan72/bashrc-cleanup). Untangles the bash/zsh relationship and removes dead OMZ weight.

• Stop sourcing ~/.bashrc from zshrc; inline the shared aliases/exports directly (Branch 3 extracts them to shared.sh)
• Remove the oh-my-zsh git plugin (custom git aliases shadow every alias it provides)
• Resolve set -o vi vs bindkey -e: drop set -o vi from bashrc so zsh uses emacs line editing consistently
• Resolve brew node vs nvm: remove brew "node" from the Brewfile so nvm manages Node versions

Why & alternatives (from explanations.txt — Branch 2)

Change	Why	Alternatives
Remove source ~/.bashrc from zshrc	Bash-specific syntax can break under zsh; mixes two shells' configs confusingly.	Use shared.sh (Branch 3).
Resolve set -o vi vs bindkey -e	bashrc set vi mode, zshrc set emacs mode. Since bashrc was sourced first, vi was immediately overridden — silent footgun.	Pick one explicitly. Emacs chosen (common even when using vim as editor).
Remove OMZ git plugin	Custom git aliases (g, gs, ga, …) shadow every OMZ alias — the plugin does nothing.	Drop custom aliases and use OMZ's instead (breaks muscle memory).
Resolve brew "node" vs nvm	Both installed → which node wins depends on PATH order. Two version managers fighting.	Picked nvm (per-project .nvmrc); brew node is simpler if version switching isn't needed.

Decision recorded: keep nvm, remove brew "node".

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Base: akan72/bashrc-cleanup. Merge order: Branch 1 → Branch 2 → Branch 3.