Add file-path context to snapshot error messages in SnapshotRequestor

[coderabbitai]

Description

The YAML parsing error handling in SnapshotRequestor::try_load and SnapshotRequestor::save methods currently collapses errors into io::ErrorKind::Other without including the file path, making debugging harder.

Location

• File: chain/rpc/src/client.rs
• Lines: around 659-661 (try_load) and 720-721 (save)

Current Behavior

When YAML parsing fails, the error message doesn't include which file caused the problem (self.file).

Expected Behavior

Error messages should include the file path and original error details to aid debugging.

References

• Related PR: feat(api): Add proper event subscription for accountUpdated #172
• Review comment: feat(api): Add proper event subscription for accountUpdated #172 (comment)
• Requested by: @tolbrino

Context

This aligns with the coding guideline: "Always provide error context in error handling code."

[linear]

HOP-556