fix electric collection progressive mode

[samwillis]

Depends on electric-sql/electric#3463, must have deps bumped to new electric client version when that is released. done

Fix progressive mode to use fetchSnapshot and atomic swap

Progressive mode was broken because requestSnapshot() injected snapshots into the stream in causally correct position, which didn't work properly with the full mode stream. This release fixes progressive mode by:

Core Changes:

• Use fetchSnapshot() during initial sync to fetch and apply snapshots immediately in sync transactions
• Buffer all stream messages during initial sync (renamed flag to isBufferingInitialSync)
• Perform atomic swap on first up-to-date: truncate snapshot data → apply buffered messages → mark ready
• Track txids/snapshots only after atomic swap (enables correct optimistic transaction confirmation)

Test Infrastructure:

• Added ELECTRIC_TEST_HOOKS symbol for test control (hidden from public API)
• Added progressiveTestControl.releaseInitialSync() to E2E test config for explicit transition control
• Created comprehensive progressive mode E2E test suite (8 tests):
  • Explicit snapshot phase and atomic swap validation
  • Txid tracking behavior (Electric-only)
  • Multiple concurrent snapshots with deduplication
  • Incremental updates after swap
  • Predicate handling and resilience tests

Bug Fixes:

• Fixed type errors in test files
• All 166 unit tests + 95 E2E tests passing

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🦋 Changeset detected

Latest commit: 2846a6e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
@tanstack/electric-db-collection	Patch
@tanstack/db-collection-e2e	Patch
@tanstack/db	Patch
@tanstack/angular-db	Patch
@tanstack/powersync-db-collection	Patch
@tanstack/react-db	Patch
@tanstack/rxdb-db-collection	Patch
@tanstack/solid-db	Patch
@tanstack/svelte-db	Patch
@tanstack/trailbase-db-collection	Patch
@tanstack/vue-db	Patch

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commit: 2846a6e

[github-actions]

Size Change: 0 B

Total Size: 86.2 kB

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Size Change: 0 B

Total Size: 3.34 kB

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[KyleAMathews]

Looks great! All that work you did on truncate is coming in handy! Very nice semantics to be able to easily do this clean swap.

[kevin-dp]

Mostly note to self during review:

Perform atomic swap on first up-to-date: truncate snapshot data → apply buffered messages → mark ready

--> Need to check that we also cancel in-flight fetchSnapshot requests and/or ignore fetchSnapshot requests that resolve after the swap.

[kevin-dp]

This is great work, i think we're almost there but i believe there is a bug with fetchSnapshot requests that resolve after the up-to-date message. For the rest i only have minor comments/nits.

[samwillis]

@kevin-dp I've addressed your review. We should still come back to this file and tidy it up more.

Discussed with Kyle, merging as is before the weekend. We can make further changes later.