[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.

[benitav]

Additional PR: powersync-ja/powersync-js#938

What's changing in this PR: This is the actual implementation PR for the JS sync client removal — it deletes ~2k lines of the JavaScript client, removes the bson dependency, and drops compatibility with PowerSync service versions 1.11.3 and older (though the PR notes the Rust client already implicitly dropped that support when it became the default).

Additional affected pages/sections: None beyond what is already listed above — the existing guidance on removing syncImplementation: 'JS' references and adding a migration note covers this PR's user-facing impact.

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