add cpp package design

[ColinLeeo]

Description

This PR proposes the initial design plan for the TsFile C++ package.

The goal of this proposal is to define the package structure, build strategy, API organization, and distribution approach for the C++ package, so that we can provide a more convenient and maintainable way for users to integrate TsFile in C++ projects.

This PR only introduces the design document for discussion. No code changes are included at this stage.

Design Scope

The proposal covers:

• C++ package structure
• Public API organization
• Build and dependency management
• Package generation and distribution strategy
• Compatibility considerations
• Future development roadmap

Discussion

This design is open for review. Please feel free to provide comments, suggestions, or alternative ideas.

Community feedback will help us refine the design before starting the implementation phase.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.47%. Comparing base (46cf0a1) to head (e92d89c).
⚠️ Report is 8 commits behind head on develop.

Additional details and impacted files

@@ Coverage Diff @@## develop #893 +/- ##
===========================================
- Coverage 60.51% 60.47% -0.04% 
===========================================
Files 744 744 Lines 49081 49142 +61 Branches 7797 7832 +35 ===========================================
+ Hits 29703 29721 +18 - Misses 17978 18025 +47 + Partials 1400 1396 -4 

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