Harden headless Git authentication and signing

.gitignore

@@ -2,5 +2,27 @@ local
 .DS_Store
 nvim/plugin/
 gh/
-.claude
-.wrangler
+.claude/
+.codex/
+.wrangler/
+homebrew/
+Brewfile.lock.json
+
+# Secrets and machine-local authentication
+.env
+.env.*
+!.env.example
+*.pem
+*.key
+*.p12
+*.secret
+credentials.json
+auth.json
+token.txt
+*-credentials
+*credential-input*
+.gitconfig.local
+gitconfig.local
+CLAUDE.local.md
+AGENTS.override.md
+.codex-global-state.json

.pre-commit-config.yaml

@@ -0,0 +1,8 @@
+# Pre-commit hooks for this public dotfiles repository.
+# Install once with: pre-commit install
+# Run against all files with: pre-commit run --all-files
+repos:
+  - repo: https://github.com/gitleaks/gitleaks
+    rev: v8.30.1
+    hooks:
+      - id: gitleaks

Brewfile

@@ -13,6 +13,7 @@ brew "neovim"
 brew "mosh"
 brew "node"
 brew "postgresql@17"
+brew "pre-commit"
 brew "py-spy"
 brew "pyenv"
 brew "tmux"

README.md

@@ -86,3 +86,9 @@ session links. The first existing settings file is retained as
 ### Tmux Plugin Manager
 - Install Tmux Plugin Manager ([Github](https://github.com/tmux-plugins/tpm#tmux-plugin-manager))
 - Install tmux packages with `prefix + I`
+
+## Headless Mac mini
+
+- [Setup and restart verification](docs/mac-mini-setup-guide.md)
+- [Tailscale SSH architecture](docs/tailscale-ssh.md)
+- [Personal/work GitHub authentication](docs/github-auth.md)

agent-instructions.md

@@ -17,3 +17,39 @@ Create pull requests with the simple format
 Single-line commands or code within a sentence should be wrapped in backticks
 
 Multi-line commands or code should use fenced code blocks with triple backticks
+
+# Git Credential Safety
+
+GitHub HTTPS authentication may be routed by URL through machine-local credential
+helpers. Use normal Git commands and let the configured helper supply credentials.
+
+- Never ask for, read, display, copy, log, or inspect a token or credential file.
+- Never run `git credential fill`, `git credential get`, or an equivalent helper
+  command that returns a secret.
+- Never extract a Git credential into `GH_TOKEN`, a command, a prompt, or a log.
+- Never run `gh auth setup-git` or modify credential routing unless the user asks
+  for that exact change.
+- Never put credentials or machine-local authentication files in a repository.
+
+Before a network Git operation, inspect the remote and selected routing without
+reading a secret:
+
+```sh
+remote="$(git remote get-url origin)"
+git config --get-urlmatch credential.helper "$remote"
+git config --get-urlmatch credential.username "$remote"
+```
+
+Stop and ask the user if the expected helper or username is missing. Do not bypass a
+missing include or repair credentials autonomously.
+
+# Git Workflow Safety
+
+- Inspect `git status --short` before editing or staging.
+- Stage explicit files; do not use `git add .`.
+- Do not commit or push unless the user explicitly requests it.
+- Fetch and inspect divergence before pushing.
+- Never force-push unless the user explicitly approves it after the risk is stated.
+- Treat a dry-run `non-fast-forward` rejection as a synchronization issue, not an
+  authentication failure.
+- Verify commit name, email, and signing identity separately from PAT routing.