refactor: consolidate all branches into single-branch Strategy 1

- bash/.bashrc: replace oh-my-bash with minimal unified config
  sources common → aliases → OS overlay → .bashrc.local

- zsh/.zshrc: remove hardcoded macOS PATHs (moved to macos overlay)
  clean sourcing order: common → personal → aliases → OS → .zshrc.local

- shell/common: populated with universal exports (EDITOR, HISTSIZE, etc.)
- shell/macos: Homebrew, Antigravity, Flutter PATH, fzf init, macOS aliases
- shell/linux: xdg-open, xclip, fzf init for Linux

- nvim/plugins/work.lua: Copilot plugin (migrated from origin/work branch)
- nvim/plugins/_init.lua: conditional load via DOTFILES_PROFILE=work env var

- tmux/.tmux.conf.local: per-machine override hook (~/.tmux.conf.machine.local)

- bootstrap.sh: one-command new machine setup with profile support
  usage: bash bootstrap.sh [personal|work]

- .gitignore: comprehensive .local file ignore patterns

All branches (linux, mac, work, linux_personal, linux_work, mac_personal)
can now be deleted — all unique content is merged into master.

tmux/.tmux.conf.local

@@ -366,6 +366,13 @@ source-file "/Users/jsarthak/dotfiles/tmux/config/keybindings.conf"
 
 setw -g window-status-separator " #[fg=#484848]• " #!important
 
+# ── Per-machine local override (untracked) ────────────────────────────────────
+# Create ~/.tmux.conf.machine.local on each machine for host-specific tweaks
+# (e.g. different color scheme, right-side content, etc.)
+if-shell 'test -f ~/.tmux.conf.machine.local' \
+  'source-file ~/.tmux.conf.machine.local'
+
+
 # -- tpm -----------------------------------------------------------------------
 
 # while I don't use tpm myself, many people requested official support so here