## Why
Memory clients sometimes need to continue reading a file from a known
line instead of starting over from the top. Adding a line offset to the
`read` MCP keeps that resume logic simple and avoids re-reading
already-consumed content.
## What changed
- Added an optional `line_offset` argument to the memory `read` tool,
defaulting to `1`.
- Read content starting at the requested 1-indexed line before token
truncation, and return `start_line_number` in the response.
- Treat invalid offsets as invalid params errors and cover the new
behavior in `codex-rs/memories/mcp/src/local_tests.rs`.
## Testing
- Added unit tests for reading from a non-default starting line.
- Added unit tests for rejecting `0` and past-end line offsets.