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.

shell/.config/shell/common

@@ -0,0 +1,13 @@
+# ── Truly shared exports / env vars ───────────────────────────────────────────
+# Sourced by both .zshrc and .bashrc on ALL machines (all OSes, all profiles).
+# Keep this minimal — only things that apply 100% universally.
+
+export EDITOR='nvim'
+export VISUAL='nvim'
+
+# Man page rendering
+export MANROFFOPT="-c"
+
+# Better history defaults (bash and zsh honour these)
+export HISTSIZE=10000
+export HISTFILESIZE=20000

shell/.config/shell/linux

@@ -0,0 +1,21 @@
+# ── Linux-specific shell config ───────────────────────────────────────────────
+# Sourced automatically from .zshrc / .bashrc on Linux hosts only.
+
+# xdg-open alias (Linux equivalent of macOS `open`)
+alias open="xdg-open"
+
+# Clipboard helpers (if xclip is present)
+if command -v xclip >/dev/null 2>&1; then
+  alias pbcopy="xclip -selection clipboard"
+  alias pbpaste="xclip -selection clipboard -o"
+fi
+
+# fzf shell integration (Linux path)
+[[ -f /usr/share/doc/fzf/examples/key-bindings.zsh ]] && \
+  source /usr/share/doc/fzf/examples/key-bindings.zsh
+[[ -f ~/.fzf.zsh ]] && source ~/.fzf.zsh
+
+# Zoxide (smarter cd) — in case not already initialized by bashrc
+if [[ -n "$ZSH_VERSION" ]]; then
+  command -v zoxide >/dev/null && eval "$(zoxide init zsh)"
+fi

shell/.config/shell/macos

@@ -0,0 +1,19 @@
+# ── macOS-specific shell config ───────────────────────────────────────────────
+# Sourced automatically from .zshrc / .bashrc on Darwin hosts only.
+
+# Homebrew
+eval "$(/opt/homebrew/bin/brew shellenv)" 2>/dev/null
+export PATH="/opt/homebrew/bin:/opt/homebrew/sbin:$PATH"
+
+# Antigravity
+export PATH="/Users/jsarthak/.antigravity/antigravity/bin:$PATH"
+
+# Flutter SDK
+export PATH="/Users/jsarthak/flutter-sdk/flutter/bin:$PATH"
+
+# fzf shell integration (macOS path)
+source <(fzf --zsh) 2>/dev/null || true
+
+# macOS convenience aliases
+alias finder="open -a Finder ."
+alias brewup="brew update && brew upgrade && brew cleanup"