docs(.github): add repo-specific instructions

.github/copilot-instructions.md

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+# GitHub Copilot Instructions for ai.jone.foo
+
+This file contains repository-specific instructions for Copilot when working on the ai.jone.foo project.
+
+## Repository Structure
+
+For file list, see index.md. This file documents Copilot-specific workflow and restrictions for ai.jone.foo.
+
+## RTK Integration
+
+Jone uses **RTK (Rust Token Killer)** via a pre-tool hook to minimize token consumption.
+
+### How it works
+
+The `.github/hooks/rtk-rewrite.json` hook intercepts bash commands at execution time:
+- Raw commands like `git status`, `grep pattern src/`, `find .` are rewritten to use `rtk`
+- This reduces command output token usage by 60-90%
+
+See AGENTS.md for RTK usage and restrictions.
+
+## Deployment Workflow
+
+### Deploy process
+
+When the user says "deploy" or wants to push changes to production, follow this exact process:
+
+1. **Commit and push to main**
+
+   ```bash
+   git add (changes, NEVER do git add -A or git add .)
+   git commit -m "scope: short description"
+   git push
+   ```
+
+2. **SSH to root@jone.foo and pull**
+   ```bash
+   ssh root@jone.foo "cd /home/caddy/ai.jone.foo && git pull"
+   ```
+
+### Important details
+
+- **User:** `root` (not `caddy`)
+- **Deploy location:** `/home/caddy/ai.jone.foo`
+- **Path expansion:** When escaping for SSH, use `\~` instead of `~` and `\;` for semicolons
+- **No intermediate script** — deploy is just `git pull` (files served directly by Caddy)
+
+### What NOT to do
+
+- Don't suggest custom deployment scripts or CI/CD
+- Don't ask for confirmation in the middle of deployment
+- When deploying, always verify the pull succeeded with a follow-up status check
+
+## Shell Context
+
+See AGENTS.md for shell context details.
+
+## What's in AGENTS.md
+
+**AGENTS.md** (in the repo root) contains **global instructions** for all Copilot sessions across all of Jone's projects:
+
+- Custom instructions (tone, language, code style)
+- **Testing rules:** never inline commands, always use proper unit tests
+- Sub-agent communication patterns
+- Security rules
+- Git and workflow preferences
+
+**DO NOT duplicate** AGENTS.md content here. Link to it if needed, but keep this file repo-specific only.
+
+## Repository conventions
+
+- **Markdown formatting:** Use vanilla markdown, no special tooling
+- **Commit messages:** Follow conventional commits (see AGENTS.md)
+- **Language:** German for docs, English for code/config
+- **No external dependencies** — keep this repo minimal
+
+## When to escalate
+
+If the user asks for:
+
+- Complex CI/CD or automation → Suggest they use `/plan` to think through it first
+- MCP servers for RTK → Clarify that the hook system already handles it
+- Caching or optimization of git pulls → Document in this file, don't implement magic