test: add E2E tests for table editor

[corvid-agent]

Summary

• Add 12 comprehensive Playwright E2E tests for the table editor component covering the full user workflow
• Tests verify table rendering, cell editing, row add/remove/reorder, markdown output, and various table sizes
• All tests pass locally alongside existing E2E tests with no regressions

Test Coverage

Test	Description
Render table	Verify imported markdown table renders correctly in structured editing mode
Edit cells	Test editing individual cells and verifying changes
Add row	Add new rows and fill in values
Remove row	Remove rows and verify remaining data
Empty state	Remove all rows and verify empty state message
Move up	Reorder rows by moving up
Move down	Reorder rows by moving down
Markdown output	Verify preview renders correct markdown after edits
Large table	Test with a 5-row, 4-column table
Special characters	Test cells with quotes, angle brackets, ampersands
Change Log table	Verify a second table in the same spec works
Full workflow	End-to-end workflow combining edit, add, reorder, and remove

Test plan

• All 12 new E2E tests pass
• All 11 existing E2E tests still pass (no regressions)

Fixes #35

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