Tables: tolerate trailing whitespace on rows; reject empty delimiter cells

[dereuromark]

Two table delimiter-row divergences where the PHP implementation was the outlier (carve-js and carve-rs agreed). Ported from carve-php commit 28d4c10.

1. Trailing whitespace on table rows

Trailing spaces or tabs after a row's closing pipe broke row recognition. A line like | a | followed by spaces, or a separator |---| followed by spaces, was not treated as a table row, so a table with a trailing-whitespace separator split into separate blocks and the separator rendered as a paragraph.

Trailing whitespace after the closing pipe is insignificant and is now stripped before the structural checks (isTableRow, isSeparatorRow, the cell parsers, and the BlockParser row loop).

2. Empty delimiter cell

A delimiter row with an empty cell (|---||) was wrongly accepted as a header separator. The detection used a character class that placed | inside it and so never validated per cell. It now splits the row into cells and requires each to be a delimiter cell (optional whitespace, optional leading colon, one or more dashes, optional trailing colon). An empty cell or any other content disqualifies the row, which then stays an ordinary data row.

Behavior now matches the JS and Rust implementations on these delimiter-row edge cases.

[codecov]

Codecov Report

❌ Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.05%. Comparing base (306e362) to head (8e8413f).

Files with missing lines	Patch %	Lines
src/Parser/Block/TableParser.php	85.71%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #247      +/-   ##
============================================
- Coverage     92.06%   92.05%   -0.01%     
- Complexity     3571     3576       +5     
============================================
  Files           107      107              
  Lines         10118    10131      +13     
============================================
+ Hits           9315     9326      +11     
- Misses          803      805       +2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.