feat: vendor official hippo memory extension

hippo-memory-pi/README.md

@@ -0,0 +1,77 @@
+# Hippo Memory - Pi Extension
+
+> **my-pi packaging note:** this official source is bundled and loaded directly by the root package; do not copy it to another Pi extension directory. Use the root `install.sh`, `update.sh`, and `uninstall.sh` prompts to manage the matching global CLI. Upstream's original manual instructions are retained below for reference.
+
+Biologically-inspired memory for [Pi coding agent](https://github.com/badlogic/pi-mono). Memories decay by default, retrieval strengthens them, errors stick longer, and sleep consolidation compresses episodes into patterns.
+
+## Install
+
+```bash
+# Install hippo CLI
+npm install -g hippo-memory
+
+# Init hippo in your project (or scan all repos)
+hippo init
+# or: hippo init --scan ~
+
+# Copy extension to Pi's extensions directory
+cp -r extensions/pi-extension ~/.pi/agent/extensions/hippo-memory
+```
+
+Or for project-level:
+```bash
+cp -r extensions/pi-extension .pi/extensions/hippo-memory
+```
+
+## What it does
+
+| Automatic | When |
+|---|---|
+| Injects memory context | Session start |
+| Captures tool errors | After any failed tool call |
+| Learns from git | On `hippo sleep` (session end) |
+| Consolidates memories | On `hippo sleep` (session end) |
+| Shares to global store | On `hippo sleep` (session end) |
+
+Error capture has three filters to prevent memory pollution:
+1. Noise pattern filter (timeouts, ECONNREFUSED, etc.)
+2. Per-session rate limit (max 5 error memories)
+3. Per-session deduplication
+
+## Tools
+
+The extension registers 5 tools for the LLM:
+
+| Tool | Description |
+|---|---|
+| `hippo_recall` | Search memories by topic |
+| `hippo_remember` | Store a new memory |
+| `hippo_outcome` | Report if memories were helpful |
+| `hippo_status` | Check memory health |
+| `hippo_context` | Smart context from git state |
+
+## Config
+
+Edit the `DEFAULT_CONFIG` object at the top of `index.ts`:
+
+```typescript
+const DEFAULT_CONFIG = {
+  budget: 4000,           // Token budget for recall
+  contextBudget: 1500,    // Token budget for auto-context
+  framing: 'observe',     // observe | suggest | assert
+  autoContext: true,       // Inject context at session start
+  autoLearn: true,         // Capture tool errors
+  autoSleep: true,         // Run consolidation on exit
+  maxErrorsPerSession: 5,  // Error capture rate limit
+};
+```
+
+## Requirements
+
+- `hippo-memory` CLI installed globally: `npm install -g hippo-memory`
+- `.hippo/` initialized in your project: `hippo init`
+- Pi coding agent
+
+## How it differs from the OpenClaw plugin
+
+Same core behavior. The Pi extension uses Pi's event system (`session_start`, `tool_result`, `session_shutdown`) instead of OpenClaw's hook system. Both use `execFileSync` with args arrays (no shell injection).