Release v0.1.7 markdown rendering

[cowboycodr]

Summary

This PR moves the v0.1.7 release work from table-rendering into main.

It includes:

• Markdown table rendering with aligned columns, styled headers, escaped pipe support, and source mapping for search and selection highlights.
• Table cell wrapping so long cells grow into additional visual rows instead of truncating.
• Internal table body separators so wrapped/body rows remain visually distinct without adding an outside top or bottom border.
• Blockquote wrapping fixes and nested blockquote marker rendering.
• Nested bullet marker alternation by indentation level.
• A broad benchmark.md Markdown fixture for renderer QA.
• GitHub Actions CI for formatting, tests, and release builds.
• The v0.1.7 release metadata in Cargo.toml, Cargo.lock, and CHANGELOG.md.

Validation

• cargo fmt --all -- --check
• cargo test --locked (124 passed)
• cargo build --release --locked
• git diff --check

Notes

The v0.1.7 tag and GitHub release already point at this branch tip (ebf9f91). This should be merged without squashing so the release tag remains on the same commit that lands in main.