chore: cut 6.20.0 release — 7 unreleased feat/fix commits on main

[rickcedwhat-ai]

Context

7 feat/fix commits landed on main after the 6.19.0 release (2026-07-21) with no [Unreleased] section in CHANGELOG.md:

• feat(filtering): support columnOverrides.read in findRow/findRows/countRows (feat(filtering): support columnOverrides.read in findRow/findRows/countRows #398)
• feat(countRows): support optional filters and maxPages override (feat(countRows): support optional filters and maxPages override #396)
• fix(playground): add cell-loading skeleton to off-screen column placeholders (fix(playground): add cell-loading skeleton to off-screen column placeholders #395)
• feat(virtualization): self-healing row locators via resolveRowIndex selector (feat(virtualization): self-healing row locators via resolveRowIndex selector (#392) #393)
• fix(virtualization): collect above-viewport overscan rows instead of deferring (fix(virtualization): collect above-viewport overscan rows (#384) #390)
• fix(dedupe): register key after callback, not before (fix(dedupe): register key after callback, not before #389)
• fix(pagination): final scan after advancePage returns false at EOF (fix(pagination): final scan after advancePage returns false at EOF #388)

Tasks

• Add [Unreleased] section to CHANGELOG.md with all 7 entries
• Bump version to 6.20.0
• Publish to npm

Found in GBU report 2026-07-29.