v2.2.0: Model interface cleanup

[mkenney]

Added

• model.Model.GetData() — returns snapshots of the data set and key/index maps; implementations must not expose internal storage directly
• model.Model.Reverse() — reverses the order of the data store
• sorter.SortByValue — zero-value SortFlag; type-stratified sort (nil < bool < numeric < string < other); now the default sort behavior
• sorter.SortAsc, SortDesc, SortAsString, SortReverse — explicit bitflag sort options
• .gitignore

Changed

• model.ModelTypeHash / model.ModelTypeList renamed to model.HASH / model.LIST; order swapped so HASH is the zero/iota value
• model.Model.Filter callback signature changed from func(Value) Model to func(Value) bool
• model.Model.Map callback signature changed from func(Value) Model to func(Value) Value
• model.Model.Reduce callback signature changed from func(Value) bool to func(carry, cur Value) Value (standard fold semantics)
• model.Model.SetID now returns error
• sorter.SortFlag underlying type changed from int to uint
• sorter.Sorter.Reverse signature changed from Reverse(SortFlag) error to Reverse() error

Fixed

• errors/error.go package declaration corrected from package error to package errors

[Copilot]

Pull request overview

This PR updates the model and sorter package interfaces/flags as part of a “model interface cleanup”, and adds a repository .gitignore.

Changes:

• Converted sorter.SortFlag to a bitmask-style flag set and adjusted the Sorter interface (notably Reverse() signature).
• Updated model.Model API (Filter/Map/Reduce signatures, added GetData() and Reverse(), and changed SetID to return an error).
• Added a root .gitignore.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 6 comments.

File	Description
sorter/sorter.go	Switches SortFlag to bit flags and updates the Sorter interface.
model/model.go	Renames/reorders ModelType constants and revises the Model interface methods/contracts.
.gitignore	Introduces ignore rules for Go/workspace artifacts and local tooling outputs.

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