nes: cleanup: unite params by semantic proximity into entities

[ulugbekna]

No description provided.

[Copilot]

Pull request overview

This PR refactors the Copilot NES (next edit suggestions) Xtab provider to reduce long parameter lists by grouping semantically related values into context “entities” (e.g., tracing, edit-stream context, response options, fetch metadata), aiming to simplify call sites and improve readability within the Xtab streaming pipeline.

Changes:

• Introduces new context interfaces (RequestTracingContext, EditStreamContext, etc.) and threads them through the provider.
• Refactors streaming entry points to pass consolidated context objects instead of many individual parameters.
• Begins introducing a local fetch cancellation token source to allow early aborts (e.g., cursor-line divergence).

Show a summary per file

File	Description
extensions/copilot/src/extension/xtab/node/xtabProvider.ts	Refactors XtabProvider streaming/request plumbing by bundling parameters into context objects and adjusting streaming/cancellation flow.

Copilot's findings

Comments suppressed due to low confidence (1)

extensions/copilot/src/extension/xtab/node/xtabProvider.ts:730

• This new _streamEditsImpl contains leftover wrapper logic: it re-declares fetchCts/fetchCancellationToken (shadowing the parameters) and then delegates to this._streamEditsImpl(...) with names that aren’t in scope here (modelServiceConfig, opts, telemetryBuilder). Besides not compiling, this also indicates two implementations of _streamEditsImpl exist (the call is targeting a different signature). Consolidate to a single _streamEditsImpl implementation (preferably the new context-based one) and keep CTS creation in exactly one place (either streamEdits or the impl).

		// Create a local cancellation source linked to the caller's token.
		// This lets us cancel the fetch immediately on cursor-line divergence
		// without reaching into the request's CancellationTokenSource (which
		// is owned by nextEditProvider.ts).
		const fetchCts = new CancellationTokenSource(cancellationToken);
		const fetchCancellationToken = fetchCts.token;

		try {
			return yield* this._streamEditsImpl(
				request, endpoint, modelServiceConfig, messages, clippedTaggedCurrentDoc,
				editWindow, editWindowLines, cursorOriginalLinesOffset, editWindowLineRange,
				promptPieces, prediction, opts, delaySession, tracer, telemetryBuilder,
				logContext, cancellationToken, originalEditWindow, fetchCts, fetchCancellationToken,
			);

• Files reviewed: 1/1 changed files
• Comments generated: 0