[FEATURE][Java] Adapt Parquet physical IO to columnar batches

### Describe the enhancement requested

After #959 / PR #961 replaces the provisional row-oriented physical-batch contract with
column vectors, the Parquet backend needs the corresponding adapter migration. This issue is one
narrow downstream slice: it must not retain a compatibility `Row` facade.

Scope:

- migrate `graphar-io-api` read-contract tests and `graphar-io-parquet` from
`RecordBatch.row(int)` / `Row` to `ValueVector` and `VectorRecordBatch`;
- preserve physical projection, strict half-open row-range reads, and required Parquet Offset Index
behavior;
- preserve safe binary/list/null value ownership at the vector boundary;
- treat `WriteMode.APPEND` explicitly: Parquet cannot atomically append to one existing file, so the
writer must reject it rather than silently overwriting.

Non-goals: migrating GraphAr reader/writer/validator/integration consumers (separate dependent
slices); adding Apache Arrow as a dependency; changing the Parquet decoding algorithm; or making
Parquet append work through a hidden rewrite.

Acceptance evidence:

1. no `Row` or `.row(...)` reference remains in `io-api` / `io-parquet`;
2. focused clean verification covers vector schema position, count, null, binary and list values;
3. canonical fixture projection/row-range tests retain applied `PROJECTION` and `ROW_RANGE`;
4. writer still emits readable Offset Indexes with the existing bounded-page assertion;
5. a write with `APPEND` is explicitly rejected, never treated as overwrite.

Component(s): Java

Relates to #947 and #959.

Start with the vector contract from #959/PR #961, then inspect the read-contract tests in graphar-io-api and the Parquet implementation in graphar-io-parquet. Run the focused clean verification and canonical projection, row-range, and writer tests. Done means no Row or .row(...) references remain, vector values and ownership are covered, Offset Index behavior is retained, and APPEND is rejected.

Written by the indexing model from the issue text.