Fix Sync Streams signed string casts

[sravan27]

Summary

Fix Sync Streams expression evaluation for SQLite-style casts from signed numeric strings. The JavaScript evaluator previously parsed only unsigned numeric prefixes, so values like CAST('-12' AS integer) and CAST('-.5' AS numeric) evaluated as 0 instead of matching SQLite.

Why this matters

Sync rules can cast request parameters or JSON/text values before filtering rows. A signed value in a parameter or source row could therefore select the wrong rows in the JavaScript evaluator compared with SQLite semantics.

Changes

• Allow optional + / - prefixes when parsing integer casts from strings.
• Allow signed decimal and exponent forms for numeric casts, including .5 / -.5.
• Add direct cast tests and scalar expression engine coverage.
• Add a changeset for @powersync/service-sync-rules.

Verification

• corepack pnpm --dir packages/sync-rules exec vitest test/src/sql_functions.test.ts --run
• corepack pnpm --dir packages/sync-rules exec vitest test/src/sync_plan/engine/engine.test.ts --run -t "javascript.*signed string casts|javascript"
• corepack pnpm --dir packages/sync-rules run build:tsc

Note: running the full scalar engine test file against local Node v23.7.0 fails in the existing SQLite-engine tests because Node's experimental node:sqlite returns object rows instead of the array rows expected by the suite. The JavaScript evaluator path and pure cast tests pass locally.

[changeset-bot]

🦋 Changeset detected

Latest commit: f840f31

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

This PR includes changesets to release 16 packages

Name	Type
@powersync/service-sync-rules	Patch
@powersync/service-core	Patch
@powersync/lib-services-framework	Patch
@powersync/service-module-mongodb-storage	Patch
@powersync/service-module-mongodb	Patch
@powersync/service-module-mssql	Patch
@powersync/service-module-mysql	Patch
@powersync/service-module-postgres-storage	Patch
@powersync/service-module-postgres	Patch
@powersync/service-module-core	Patch
@powersync/service-image	Patch
test-client	Patch
@powersync/service-rsocket-router	Patch
@powersync/lib-service-mongodb	Patch
@powersync/lib-service-postgres	Patch
@powersync/service-schema	Patch

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