feat(format): preserve pipe table rows

[barrettruth]

Closes #129.

Summary

• Add is_pipe_table_row heuristic to the formatter: lines that start and end with | (after trimming trailing whitespace) are preserved verbatim
• Both the reflow entry point and the emit_prose_paragraph collector now skip pipe table rows
• Covers padded (| cell | cell |) and tight (|cell|cell|) GFM-style tables
• Add 5 unit tests: padded, tight, adjacent prose isolation, idempotency, and prose-after-table reflow
• Update site docs: formatter.mdx (preserves list) and grammar.mdx (new Pipe Tables section)

Context

The formatter was destroying every GFM pipe table in any vimdoc file — fzf-lua's 207 table lines were reflowed into unreadable garbage. The root cause: pipe table rows are unindented, tab-free LineKind::Text lines, so they hit the prose reflow path.

The heuristic has zero false positives on the combined Neovim (135 files) and Vim (155 files) runtime corpus. The only | -prefixed lines in those docs are inside code blocks (already protected) or short taglink-only lines that don't need reflow.

Traditional vimdoc tables (tab-aligned columns with ~ headers) were already safe — the existing contains('\t') check handles them.

Test plan

• cargo fmt --check passes
• cargo clippy -- -D warnings passes
• cargo test — all 142 tests pass (71 unit + 3 corpus + 7 format CLI + 50 integration + 11 server)
• prettier --check site/ passes
• Formatter on fzf-lua doc: zero table lines changed (was 498 lines mangled before)

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Project	Deployment	Actions	Updated (UTC)
vimdoc-language-server	Ready	Preview, Comment	Apr 4, 2026 4:48pm