feat: support concurrent chunk uploads

[TorstenDittmann]

This PR updates the Web SDK to support concurrent chunk uploads.

[greptile-apps]

Greptile Summary

This PR rewrites the chunked upload path in src/client.ts to dispatch up to 8 chunks concurrently after uploading the first chunk sequentially to obtain the upload ID, and adds setKey and setForwardedUserAgent helpers along with a version bump to 25.2.0.

• The concurrent upload orchestration (first-chunk sequencing, shared rejected/completedCount state, and Promise-based concurrency gate) is correct for JavaScript's single-threaded execution model and should work reliably against Appwrite's synchronous server-side assembly.
• ping() return type was widened from Promise<string> to Promise<unknown>, which is a breaking TypeScript API change for consumers that typed the return value.
• finalResponse ?? lastResponse relies on isUploadComplete firing for the assembled-file response; if it doesn't (edge-case server behavior), the returned value is the chronologically last chunk response, which is non-deterministic in concurrent mode.

Confidence Score: 5/5

The concurrent upload logic is structurally sound; the two new observations are cosmetic or edge-case concerns that do not affect normal operation.

The core concurrency change is correct: first chunk is uploaded sequentially to get the upload ID, remaining chunks are dispatched with an in-flight cap, shared counters are safe under JS's single-threaded model, and failure propagation is handled cleanly. The two findings are a type-widening regression in ping() and a defensive fallback that only matters if the server returns an unexpected response shape.

src/client.ts — the isUploadComplete predicate and finalResponse ?? lastResponse fallback are worth a second look to confirm they match the server's actual response shape for assembled files.

Important Files Changed

Filename	Overview
src/client.ts	Adds concurrent chunk uploads (up to 8 in-flight), setKey/setForwardedUserAgent helpers, and flips x-sdk-platform to 'server'; the concurrent upload logic is sound for the happy path but has an edge-case non-deterministic fallback return value when isUploadComplete never fires.
package.json	Version bump from 25.1.1 to 25.2.0, no other changes.
package-lock.json	Lock-file version bump to match package.json, no dependency changes.

_{Reviews (2): Last reviewed commit: "feat: support concurrent chunk uploads" | Re-trigger Greptile}

[TorstenDittmann]

Note for reviewers: the normal cloud sdks task currently cannot generate sdk-for-web as a client SDK because CE config lists web under APP_SDK_PLATFORM_SERVER, and the generator sets x-sdk-platform from the enclosing platform key via setPlatform($key). Generating through that path produces server-only drift like x-sdk-platform: server, API key headers, forwarded user agent, and server ping behavior. This Web SDK update should be generated with explicit platform=client output so the package remains the browser/client SDK.

[TorstenDittmann]

@greptile-apps please review this PR again.