fix: ndjson file type detection (#4349)
This PR fixes a bug where njson detection misclassifies multiline single
json files as ndjson.
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---
> [!NOTE]
> **Medium Risk**
> Changes JSON/NDJSON detection heuristics and `detect_filetype`
routing, which can affect which partitioner is invoked for JSON-like
inputs. The logic is more strict and covered by new edge-case tests, but
misclassification could still impact downstream parsing behavior.
>
> **Overview**
> Fixes NDJSON file-type detection so **multi-line single JSON objects**
(including `.json` and `.ipynb` notebook payloads) are no longer
misrouted to `partition_ndjson` and crashing.
>
> Updates `is_ndjson_processable` to require the *first line* to
independently parse as a JSON object (with special handling for
potentially truncated long single-line records), adds a bounded read
helper (`json_disambiguation_text`) for disambiguation beyond the 4KB
`text_head`, and changes JSON/NDJSON disambiguation to default to
`FileType.JSON` when NDJSON criteria aren’t met.
>
> Adds a focused test suite for these NDJSON edge cases, bumps version
to `0.22.27`, updates the changelog, and makes CI apt installs more
resilient by wrapping them in a retry helper.
>
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
e82dbd7d017e2a1f1d5406ad8ca887109b3c5553. Bugbot is set up for automated
code reviews on this repo. Configure
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