v1.16.2

## Highlights
- Adds observation lifecycle state derived from `review_after`.
- Adds `mem_review` for listing memories that need review and marking one reviewed.
- Adds Pi-native review support through the Engram HTTP server for `gentle-engram`.
- Pins critical observations in context so important memory is harder to bury.

## Changes

### Memory lifecycle
- Surface computed observation state as `active` or `needs_review`.
- Add store-level review queries and local-only review reset behavior.
- Expose lifecycle metadata through MCP save/search responses.

### MCP, HTTP, and Pi
- Add MCP `mem_review` for direct agent integrations.
- Add HTTP review routes used by `gentle-engram` Pi-native tools.
- Add compact Pi chrome for review list and mark-reviewed flows.

### TUI and docs
- Show lifecycle state in the TUI list/detail views.
- Document `mem_review`, lifecycle metadata, HTTP routes, and Pi setup behavior.

## Install
```bash
brew upgrade engram
```

## Compatibility notes
- `mark_reviewed` resets the local review cycle only; lifecycle review timestamps are not synced yet.
- Pi users should pair this with `gentle-engram@0.1.8` for native `mem_review` support.