fix: buffer too short should fail

[adrienaury]

No description provided.

[Copilot]

Pull Request Overview

This pull request fixes an issue where a buffer that is too short now correctly triggers a failure. The key changes include:

• Adding a new error variable (ErrIncompleteBuffer) and updating the buffer growth function to detect incomplete buffers.
• Tweaking error messages in the unfold command for improved clarity.
• Refactoring the fold command to delegate the execution loop into a new helper function (execUntilEOF) to better handle EOF and error propagation.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pkg/posimap/core/buffer/buffer.go	Added a new error for incomplete buffers and updated growTo for stricter read length checks.
internal/appli/command/unfold.go	Updated error messages for buffer preparation for consistency.
internal/appli/command/fold.go	Refactored the record handling loop into execUntilEOF and updated error handling.

Comments suppressed due to low confidence (1)

internal/appli/command/fold.go:85

• [nitpick] Consider using a consistent variable name for the record object; currently, the call uses 'record' while the execUntilEOF function defines the parameter as 'rcrd'.

if err := f.execUntilEOF(cfg, reader, writer, record); err != nil {