dotfiles: initial scaffold for Coder devboxes

install.sh (symlink home/* + merge-seed ~/.claude.json onboarding), gitconfig,
bash_aliases, global gitignore, inputrc, tmux.conf. Golden owns tools+starship;
this owns personal config. Secrets stay in Coder user-secrets.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

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+# dotfiles
+
+Personal dotfiles for Coder devboxes (and anywhere else). Applied automatically
+on every workspace start via Coder's dotfiles feature — the template runs
+`coder dotfiles -y "$dotfiles_uri"`, which clones this repo and runs `install.sh`.
+
+## What's here
+- `install.sh` — bootstrap: symlinks everything under `home/` into `$HOME`
+  (backing up any real file to `*.pre-dotfiles`), then merge-seeds `~/.claude.json`
+  so Claude Code skips its first-run onboarding.
+- `home/.gitconfig` — git identity + aliases + sane defaults.
+- `home/.bash_aliases` — shell shortcuts (auto-sourced by Debian's `.bashrc`).
+- `home/.config/git/ignore` — global gitignore.
+- `home/.inputrc` — readline niceties (prefix history search, smart completion).
+- `home/.tmux.conf` — tmux defaults.
+
+## Division of labour
+**Golden image** owns the system: tools (claude, kubectl, docker, helm), the
+shell framework (starship, mise, eza, zoxide, fzf), VS Code settings. **This repo**
+owns only *personal* config layered on top — it never re-installs tools or fights
+golden's starship. Secrets never live here; they go in Coder **user secrets**
+(e.g. `CLAUDE_CODE_OAUTH_TOKEN`).
+
+## Use
+Set the workspace's **Dotfiles repo** parameter (`dotfiles_uri`) to this repo's
+URL when creating a devbox. `install.sh` is idempotent — safe to re-run.