Add markdown-table-wrap-pretty: display-only pretty rendering of pipe tables

[SayreBlades]

Summary

Adds markdown-table-wrap-pretty.el — a new, opt-in display companion package that renders markdown and org pipe tables as a wrapped, Unicode box-drawing "pretty" view on top of the canonical raw table text, and toggles between that view and the editable source in place. It is the table analogue of org-latex-preview (or inline image previews).

markdown-table-wrap.el is unchanged. The new file is a separate package (Package-Requires: ((emacs \"28.1\") (markdown-table-wrap \"0.2.0\"))) that depends only on the engine's public API.

Why display-only (not buffer mutation)

markdown-table-wrap wraps a long cell into multiple | ... | rows, but pipe-table syntax has no row-spanning, so any real renderer (cmark-gfm, pandoc, GitHub, org HTML export) sees N independent data rows, not one wrapped cell. Mutating the buffer looks right in Emacs but is semantically broken the moment the text leaves Emacs. This keeps the buffer canonical — export/copy/share/push always see a real table — and makes the pretty rendering a disposable display layer:

• one display overlay per raw line (so C-n walks raw lines, big tables scroll);
• editing auto-reveals the raw source via modification-hooks (the org-latex-preview pattern — not read-only, which would break undo);
• resize re-renders pretty tables losslessly from canonical (never unwrap).

This is the display-only successor to the closed #4 (which mutated the buffer), and the read-only complement to #2: #2 is about safely rewriting table text; this is about displaying a pretty rendering over canonical text without rewriting it.

What's included

• markdown-table-wrap-pretty.el — the package: commands (-toggle/-buffer/-region), a buffer-local minor mode, defcustoms, and the renderer. Supports GFM + org (|---+---| separators and width cookies normalized for rendering only; #+TBLFM: lines left untouched). Detection is universal/line-based (no tree-sitter dep), so it works in markdown-mode, gfm-mode, md-ts-mode, and org-mode.
• test/markdown-table-wrap-pretty-test.el — 32 ERT tests for the pure helpers (parsing, row/separator rendering in plain + Unicode forms, inline-span styling, org normalization, prefix-aware display groups).
• Makefile — compile/lint/check-parens/test generalized to cover both packages; lint-package now refreshes archives so real package dependencies resolve.
• README.org — documents the optional display layer (commands, customization, install/keys).

make check (compile + checkdoc + package-lint + tests) is green: 199 tests pass (1 pre-existing expected failure in the core).

Notes / open questions

• Detection duplicates Help editor integrations rewrite Markdown tables without drifting or hanging #2. This carries its own markdown-table-wrap-pretty--table-bounds/--table-regions. Once Help editor integrations rewrite Markdown tables without drifting or hanging #2 (helper-table-inspection) lands markdown-table-wrap-table-bounds/-regions, these should delegate to the upstream functions. Built to merge independently now; happy to de-dup after Help editor integrations rewrite Markdown tables without drifting or hanging #2.
• Org scope. The engine's README is GFM-only; this ships org support too (already built and tested). If you'd prefer GFM-only for a first cut, --normalize-org-line is the one isolated piece to drop.
• Co-packaging on MELPA. Both files ship from one repo; with the current MELPA recipe (markdown-table-wrap) the pretty file rides along (autoloaded, minor mode off by default → no behavior change for existing users). If you'd prefer it as a separately-installable/versioned package, it just needs its own MELPA recipe.
• I dropped an unused max-cell-height defcustom that existed in the prototype but was never wired into rendering (the public markdown-table-wrap-cell takes no height cap). Easy to re-add as a real feature if wanted.

Happy to split org support out, adjust naming/keys, or rebase detection onto #2's branch.