feat(tables): add phase 2 table features

[YousefHadder]

This PR implements Phase 2 table features including:

• Transpose table (tt) - Swap rows and columns
• Sort by column (tsa/tsd) - Sort ascending/descending
• CSV conversion (tvx/tvi) - Export to CSV and import from CSV
• Cell alignment (ta) - Toggle left/center/right alignment
• Clear cell (tx) - Clear cell content
• Move rows (tmj/tmk) - Move row down/up
• Move columns (tmh/tml) - Move column left/right

All features include:

• Full test coverage (60 table tests, 316 total tests passing)
• Comprehensive documentation (README, vimdoc)
• Type annotations (LuaCATS)
• Configuration option for destructive operations (confirm_destructive)

Quality checks:

• ✅ Lint: 0 warnings/0 errors
• ✅ Format: Clean
• ✅ Tests: 316/316 passing

[Copilot]

Pull Request Overview

This PR adds Phase 2 table manipulation features to markdown-plus.nvim, introducing advanced table operations beyond basic CRUD. The changes include cell operations (alignment toggling, clearing), row/column movement, table transformations (transpose, sort), and format conversion (CSV ↔ table).

• Cell operations: toggle alignment, clear content
• Row/column movement: swap with adjacent rows/columns
• Advanced operations: transpose, sort by column (numeric/alphabetic)
• Format conversion: bidirectional CSV ↔ markdown table conversion

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
spec/minimal_init.lua	Improved test environment setup with better plenary.nvim discovery and explicit plugin loading
spec/markdown-plus/table_spec.lua	Added comprehensive test coverage for Phase 2 table manipulation features
lua/markdown-plus/types.lua	Added confirm_destructive configuration field for destructive operations
lua/markdown-plus/table/manipulation.lua	Implemented cell alignment, row/column movement, and cell clearing operations
lua/markdown-plus/table/keymaps.lua	Registered keymaps and <Plug> mappings for new table operations
lua/markdown-plus/table/init.lua	Exposed new table manipulation functions in the public API
lua/markdown-plus/table/conversion.lua	New module for CSV/table format conversion with proper quoting/escaping
lua/markdown-plus/table/calculator.lua	New module for transpose and sort operations with numeric detection
lua/markdown-plus/config/validate.lua	Added validation for confirm_destructive configuration option
doc/markdown-plus.txt	Documented new keymaps and configuration option
README.md	Updated documentation with new keymaps and configuration

[Copilot]

Pull Request Overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.