feat(pi): pi-automaton.sh startup context printer for Pi Dev

Pi Dev doesn't auto-load automaton's system prompt (unlike opencode),
so the agent has no awareness of tasks, phases, or status.py commands.
This bridges that gap:

- scripts/pi-automaton.sh: NEW — detects scope (framework/project),
  reads active tasks, default model, config snippet, AGENTS.md rules,
  and prints a formatted context block the user pastes as their first
  message to the Pi Dev agent. Does NOT launch pi.
- scripts/register-guards.sh: EXTENDED — after Pi Dev guard install,
  offers to symlink pi-automaton.sh to ~/bin/pi-automaton
  (interactive prompt only when stdin is a terminal).
- README.md: added 'Using Pi Dev with automaton' FAQ subsection
  documenting the context printer workflow.

README.md

@@ -215,6 +215,27 @@ python3 ~/.automaton/scripts/status.py --install-schedule my-loop \
   --interval 3600 --project /path/to/project
 ```
 
+### Using Pi Dev with automaton
+Pi Dev has the `automaton-guard-pi` plugin (installed by `register-guards.sh`) which blocks edits outside allowed phases. However, Pi Dev does **not** auto-load automaton's system prompt (unlike opencode). For the agent to understand tasks and phases, provide context manually.
+
+**Before starting a Pi Dev session**, run the context printer:
+```bash
+bash ~/.automaton/scripts/pi-automaton.sh
+```
+Or if symlinked to `~/bin/`:
+```bash
+pi-automaton
+```
+
+Copy the output and paste it as your first message to the Pi Dev agent. This tells the agent about:
+- The automaton workflow framework and phase lifecycle
+- Active tasks in the current project
+- The default model and VRAM configuration
+- Project-specific rules from `AGENTS.md`
+- Which commands to use for transitions and task creation
+
+The `automaton-guard-pi` plugin still blocks edits outside `implement`/`doc_review` even without this context — the context printer just makes the agent *aware* of why it's being blocked and how to use the framework correctly.
+
 ---
 
 ## The Autopilot Workflow