Initial chezmoi-managed dotfiles with bootstrap scripts

- Rename master to legacy-2025 on remote (frozen pre-chezmoi snapshot)
- New orphan 'main' branch with bootstrap-enabled config
- .chezmoi.yaml.tmpl detects os_family (debian | arch) from /etc/os-release
- dot_zshrc.tmpl refactored from current miche config with os_family
  conditional for pacman vs apt aliases
- dot_config/: bat, btop, ghostty (with gruvbox themes), kitty (with gruvbox
  colors), nvim (LazyVim), paru
- dot_gitconfig.tmpl, dot_tmux.conf (verbatim from current state)
- run_once_00-install-bootstrap-tools.sh.tmpl: age, git, curl, ca-certificates
- run_once_10-add-chaotic-aur.sh.tmpl (arch-only): add Chaotic-AUR + install paru
- run_once_20-install-user-packages.sh.tmpl: zsh, tmux, neovim (with version
  check + binary tarball fallback for debian), oh-my-zsh + plugins, tpm,
  rustup, all CLI tools
- run_onchange_30-ensure-cargo.sh.tmpl: rustup fallback
- README.md with onboarding runbook

dot_config/nvim/lua/plugins/opencode.lua

@@ -0,0 +1,47 @@
+return {
+  "NickvanDyke/opencode.nvim",
+  dependencies = {
+    -- Recommended for `ask()` and `select()`.
+    -- Required for `snacks` provider.
+    ---@module 'snacks' <- Loads `snacks.nvim` types for configuration intellisense.
+    { "folke/snacks.nvim", opts = { input = {}, picker = {}, terminal = {} } },
+  },
+  config = function()
+    ---@type opencode.Opts
+    vim.g.opencode_opts = {
+      -- Your configuration, if any — see `lua/opencode/config.lua`, or "goto definition" on the type or field.
+    }
+
+    -- Required for `opts.events.reload`.
+    vim.o.autoread = true
+
+    -- Recommended/example keymaps.
+    vim.keymap.set({ "n", "x" }, "<C-a>", function()
+      require("opencode").ask("@this: ", { submit = true })
+    end, { desc = "Ask opencode…" })
+    vim.keymap.set({ "n", "x" }, "<C-x>", function()
+      require("opencode").select()
+    end, { desc = "Execute opencode action…" })
+    vim.keymap.set({ "n", "t" }, "<C-.>", function()
+      require("opencode").toggle()
+    end, { desc = "Toggle opencode" })
+
+    vim.keymap.set({ "n", "x" }, "go", function()
+      return require("opencode").operator("@this ")
+    end, { desc = "Add range to opencode", expr = true })
+    vim.keymap.set("n", "goo", function()
+      return require("opencode").operator("@this ") .. "_"
+    end, { desc = "Add line to opencode", expr = true })
+
+    vim.keymap.set("n", "<S-C-u>", function()
+      require("opencode").command("session.half.page.up")
+    end, { desc = "Scroll opencode up" })
+    vim.keymap.set("n", "<S-C-d>", function()
+      require("opencode").command("session.half.page.down")
+    end, { desc = "Scroll opencode down" })
+
+    -- You may want these if you stick with the opinionated "<C-a>" and "<C-x>" above — otherwise consider "<leader>o…".
+    vim.keymap.set("n", "+", "<C-a>", { desc = "Increment under cursor", noremap = true })
+    vim.keymap.set("n", "-", "<C-x>", { desc = "Decrement under cursor", noremap = true })
+  end,
+}