feat: comp-3 codec

[adrienaury]

No description provided.

[Copilot]

Pull Request Overview

Adds support for packed decimal (COMP-3) encoding throughout POSIMAP.

• Introduce Comp3 codec implementation with encode/decode logic and tests.
• Extend Field model and commands to select COMP-3 via codec: COMP-3 and picture:.
• Update String codec padding logic, add command test data, update docs and changelog.

Reviewed Changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
pkg/posimap/core/codec/string.go	Extract space‐fill byte into zero, use in padding loop
pkg/posimap/core/codec/comp3.go	New Comp3 type, errors, encode/decode logic
pkg/posimap/core/codec/comp3_test.go	Tests for COMP-3 encode/decode
internal/appli/config/model.go	Add Picture & Codec to Field, COMP-3 branch
internal/appli/config/picture.go	Parse COBOL-style picture into PictureFormat
internal/appli/config/picture_test.go	Tests for picture compilation
internal/appli/command/unfold_test.go	Register new unfold test case for COMP-3
internal/appli/command/fold_test.go	Register new fold test case for COMP-3
internal/appli/command/testdata/.../13-comp3	Add fold/unfold test fixtures for COMP-3
README.md	Document COMP-3 support
CHANGELOG.md	Note v0.3.0 COMP-3 feature

Comments suppressed due to low confidence (3)

pkg/posimap/core/codec/string.go:39

• [nitpick] The field name zero is misleading since it holds the space fill byte. Consider renaming to padByte or spaceByte to clarify its purpose.

zero    byte

pkg/posimap/core/codec/string.go:96

• You cannot range over an int. Replace with a classic for-loop, e.g., for idx := 0; idx < s.length-len(bytes); idx++ {.

for idx := range s.length - len(bytes) {

internal/appli/config/model.go:121

• Dereferencing f.Trim without checking for nil can panic. Consider defaulting to false when f.Trim is nil.

record = record.WithField(f.Name, codec.NewString(charset, f.Length, *f.Trim), f.CompileOptions()...)