* origin/main:
  feat(tui): Two-column layout with detail preview (hmans#42)
  feat: add ETag support for optimistic concurrency control (hmans#59)
  feat(plugin): improve OpenCode plugin robustness with availability checks (hmans#58)
  feat(cli): Add --prefix flag to create command (hmans#56)
  chore: clean up README.md
  docs: only push prime if it exists (hmans#52)
  fix: normalise short IDs when storing relationship links (hmans#50)

## Summary

Adds CLI flags and GraphQL mutations for partial body modifications,
enabling agents to update bean content without direct file access.
Builds on #59 (ETag support) and supersedes #57.

## Changes

### CLI: Body Modification Flags
- `--body-replace-old` / `--body-replace-new` for exact text replacement
(must match exactly once)
- `--body-append` for appending content (supports stdin with `-`)
- Mutual exclusivity with existing `--body`/`--body-file` flags

### GraphQL: Partial Body Mutations
- `replaceInBody(id, old, new, ifMatch)` - replace exactly one
occurrence of text
- `appendToBody(id, content, ifMatch)` - append content with blank line
separator
- Both support `ifMatch` for optimistic locking

### Shared Logic
- Extract `ReplaceOnce` and `AppendWithSeparator` to
`internal/bean/content.go`
- Reused by both CLI and GraphQL resolvers

### Documentation
- Add GraphQL API section to README with examples

## Usage

```bash
# CLI: Check off a task
beans update <id> --body-replace-old "- [ ] Task" --body-replace-new "- [x] Task"

# CLI: Append notes
beans update <id> --body-append "## Notes\n\nSome notes"

# GraphQL: Check off a task
beans query 'mutation { replaceInBody(id: "bean-xxx", old: "- [ ] Task", new: "- [x] Task") { body } }'

# GraphQL: Append content
beans query 'mutation { appendToBody(id: "bean-xxx", content: "## Notes") { body } }'
```

## Why This Matters for Agents

Agents can now modify bean bodies entirely through CLI/GraphQL without
needing:
- Direct file access to the `.beans/` directory
- Knowledge of where beans are stored (which can be configured outside
the repo)
- Special file permissions

## Testing

- Comprehensive tests for shared logic in
`internal/bean/content_test.go`
- GraphQL resolver tests for both mutations
- CLI tests updated for new behavior

---------

Co-authored-by: Hendrik Mans <[email protected]>