[Drift] JS sync client removed (breaking), raw tables promoted to stable, new OPFSWriteAheadVFS (powersync-js #929)

[benitav]

What shipped: Three significant changes are bundled in the upcoming JS SDK release: (1) Breaking — the JavaScript sync client has been removed from @powersync/common, @powersync/web, and @powersync/react-native; the Rust client is now the only option. (2) The "experimental" label has been removed from the raw tables feature, marking it as stable. (3) A new WASQLiteVFS.OPFSWriteAheadVFS has been added to @powersync/web, supporting concurrent reads alongside writes.

Why this needs docs: Breaking change (JS sync client removal requires user action), maturity milestone (raw tables is now stable), and new user-facing addition (new VFS option with concurrent read support).

Likely affected pages/sections:

• Web SDK / React Native SDK configuration reference — remove any reference to syncImplementation: 'JS' or the JavaScript sync client option; add a migration note for users who had it configured
• Raw tables documentation — remove the "experimental" warning/badge; update any caveats that referenced its experimental status
• Web SDK VFS options page — document WASQLiteVFS.OPFSWriteAheadVFS and its concurrent read capability; compare with existing VFS options
• Migration guide — add an entry for the JS sync client removal with upgrade instructions

Source PR: powersync-ja/powersync-js#929

CC: @benitav @stevensJourney

[simolus3]

Breaking — the JavaScript sync client has been removed from @powersync/common, @powersync/web, and @powersync/react-native; the Rust client is now the only option.

Worth noting that we don't consider this to be a breaking change, it doesn't affect the public API and we consider the used client an implementation detail.