feat(input, kpoints): support shifted kspacing mesh with koffset and kmesh_type

[Cstandardlib]

Linked Issue

Refs #7242

Description

This PR adds shifted k-point mesh support for the kspacing workflow.

Previously, when kspacing > 0, ABACUS always generated a Gamma mesh with fixed offset 0 0 0.
Now users can configure both mesh type and offset for auto-generated K_POINTS.

What's changed?

1. Added new INPUT parameters:

   • koffset: 3 real values, default 0.0 0.0 0.0
   • kmesh_type: gamma or mp, default gamma

2. Extended input parsing and validation:

   • koffset must provide exactly 3 values
   • kmesh_type accepts gamma/mp (case-insensitive handling, normalized internally)

3. Updated kspacing auto K_POINTS generation:

   • mesh type is selected by kmesh_type
   • offsets come from koffset instead of hardcoded 0 0 0

4. Updated documentation with new options

Unit Tests and/or Case Tests for my changes

• Add klist unit tests for shifted gamma/mp paths

Any changes of core modules?

• Default kspacing behavior remains unchanged.
• kspacing branch now supports configurable mesh type and offset.

[Copilot]

Pull request overview

Adds configurable shifted automatic k-point meshes for the kspacing workflow by introducing koffset and kmesh_type, and updates documentation/tests accordingly.

Changes:

• Added new INPUT parameters koffset (3 reals) and kmesh_type (gamma/mp) with parsing/validation.
• Updated kspacing auto-generated K_POINTS to use the configured mesh type and offset.
• Added unit tests for shifted Gamma and Monkhorst-Pack paths; updated docs.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
source/source_io/module_parameter/read_input_item_system.cpp	Registers/parses koffset and kmesh_type input items.
source/source_io/module_parameter/input_parameter.h	Adds koffset and kmesh_type to Input_para.
source/source_cell/klist.cpp	Uses kmesh_type and koffset when writing auto K_POINTS for kspacing.
source/source_cell/test/klist_test.cpp	Adds/updates tests to cover shifted Gamma/MP meshes under kspacing.
docs/parameters.yaml	Documents new parameters (and includes other OFDFT doc changes).
docs/advanced/input_files/input-main.md	Adds new parameter sections for koffset/kmesh_type (but also alters OFDFT docs).

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