fix: Mitigate extension host crash from Qdrant batch deletes

[daniel-lxs]

This PR fixes issue #5516, where the extension host would crash due to repeated "Bad Request" errors from the Qdrant deletePointsByMultipleFilePaths function.

The root cause was large batches of file deletion requests overwhelming the Qdrant API, with no retry logic or graceful error handling to prevent a crash loop.

Key changes in this PR include:

• Chunking: The deletePointsByMultipleFilePaths function in qdrant-client.ts now splits large deletion requests into smaller, more manageable chunks.
• Retry with Exponential Backoff: Each chunk benefits from a retry mechanism, making the process more resilient to transient API failures.
• Graceful Error Handling: The scanner.ts and file-watcher.ts services now log errors from failed chunks and continue processing, preventing the extension from crashing. A consolidated error is thrown at the end if any chunks failed permanently.
• Comprehensive Unit Tests: New tests were added to qdrant-client.spec.ts to validate the new chunking, retry, and error-handling logic.

Closes #5516

[delve-auditor]

✅ No security or compliance issues detected. Reviewed everything up to 92a05d7.

Security Overview

• 🔎 Scanned files: 4 changed file(s)

Detected Code Changes

Change Type	Relevant files
Bug Fix	► file-watcher.ts     Add error logging for batch deletions ► scanner.ts     Continue processing on deletion errors ► qdrant-client.ts     Implement chunked deletion with retries ► ChatTextArea.tsx     Update UI component handling ► IndexingStatusBadge.tsx     Refine status indicator display

Reply to this PR with @delve-auditor followed by a description of what change you want and we'll auto-submit a change to this PR to implement it.