some project-based feature bug fix

[Emt-lin]

Bug

1. the old project context cache file isn't deleted when cache updated.
2. the context cache doesn't be updated when the source file updated.
3. Since All those API(url、pdf api) calls are slow and expensive, so need to refactor project caching functionality.

Fixed

1. Fixed issues with item 1 and item 2.
2. Refactor project caching functionality.

• 1.new cache structure.

    export interface ContextCache {
       markdownContext: string;
       webContexts: Record<string, string>; // URL -> context
       youtubeContexts: Record<string, string>; // URL -> context
       timestamp: number;
       markdownNeedsReload: boolean;
    }

• 2.When the project configuration changed, markdownContext、webContexts/youtubeContexts will be processed differently

  • markdownContext: all markdownContext cache will be deleted.
  • webContexts/youtubeContexts: Remove context for URLs that no longer exist.

• 3.Load project context steps

  • markdownContext: Only process if markdownNeedsReload flag is true or there is no existing content
  • webContexts/youtubeContexts: For each url, fetch from cache if available; otherwise, make API call load context.

[logancyang]

You should create the PR against 2.9.0-preview, not master. Check #1399

[Emt-lin]

@logancyang wait review

[logancyang]

Could you list what's been done in the PR in the description?

[Emt-lin]

@logancyang wait review.

[logancyang]

@Emt-lin sorry for the late reply. Can you submit this PR to the private repo?

[Emt-lin]

@Emt-lin sorry for the late reply. Can you submit this PR to the private repo?

yeah. Recently on vacation, resubmission after the holidays.

[Emt-lin]

will resubmit this PR in the preview repo