Add `ReadFileError` and `DecodeColumnError` wrappers to provide better context for decoding errors

[wjones127]

Currently, errors that happen when decoding a column are missing information about:

1. What column that is
2. What file we are reading

This context is available higher up in the call stack that the main error is generate. We can add additional context by adding wrapper errors.

This approach is described nicely in https://sabrinajewson.org/blog/errors.

Basically, want to do things like:

enum DecodeError {
    NumberOutOfRange,
    ...
}

struct DecodeFieldError {
    field_name: String,
    field_id: i32,
    offset: u64,
    source: DecodeError,
}

fn decode(field: Field, data: Bytes) -> Result<_, DecodeFieldError> {
    ...
}

enum ReadFileErrorKind {
    IO(ObjectStoreError),
    Decode(DecodeFieldError),
}

struct ReadFileError {
    path: Path,
    kind: ReadFileErrorKind,
}

fn read_file(path: Path) -> Result<_, ReadFileError> {
    let data = read_data(path)?;
    for field in data.schema() {
        decode(field, data).map_err(|err: DecodeFieldError| {
            ReadFileError { path, kind: ReadFileErrorKind::Decode(err) }
        });
    }
}

And then the error stack would look like:

Error: failed to read file 'data.lance'

Caused by:
    0: failed to read field 'age' (id: 10) for row offset 10
    1: number out of range

[koriyoshi2041]

I'd like to work on this. My plan is to:

1. DecodeFieldError (in lance-encoding/src/decoder.rs) — a wrapper struct with field_name: String, field_id: i32, and source: Error. Implements Display as "failed to decode field '{name}' (id={id})" and chains to the source error via std::error::Error::source().

2. ReadFileError (in lance-file/src/reader.rs) — a wrapper struct with path: Path and source: Error. Implements Display as "failed to read file '{path}'" and chains to the source.

3. Wrapping points:

   • DecodeFieldError is applied via .map_err() in CoreFieldDecoderStrategy::create_structural_field_scheduler and create_legacy_field_scheduler at the points where child fields are iterated — this covers Struct, List, FixedSizeList, and Map types in both encoding paths.
   • ReadFileError is applied at FileReader::read_tasks and read_stream_projected_blocking, which are the main entry points for reading data. The FileReader struct now stores the file path.

Both types implement From<...> for Error so they integrate into the existing lance_core::Error ecosystem.

I have a PR ready — submitting now.