feat: send pinned context button immediately with pending state

[XiaoxuanLu]

Problem

In large workspaces, indexing can take a long time with no indication of status. Also, the "Pin Context" button does not appear until after indexing is complete.

Solution

The "Pin Context" is triggered immediately on startup by sending a file, folder, code, and workspace placeholder set to pending (aws/mynah-ui#421). Then, files/folders, code, and workspace are updated to active once their respective indexing processes are complete.

Should be merged after (first) aws/language-server-runtimes#687 and aws/mynah-ui#421

This pr is a replace of #2060

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 67.56757% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.42%. Comparing base (30b33a1) to head (8c99f00).

Files with missing lines	Patch %	Lines
...ver/agenticChat/context/contextCommandsProvider.ts	73.33%	8 Missing ⚠️
...nguage-server/agenticChat/agenticChatController.ts	0.00%	2 Missing ⚠️
...sperer/src/shared/localProjectContextController.ts	50.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2353   +/-   ##
=======================================
  Coverage   62.42%   62.42%           
=======================================
  Files         266      266           
  Lines       59107    59143   +36     
  Branches     3790     3796    +6     
=======================================
+ Hits        36895    36920   +25     
- Misses      22137    22148   +11     
  Partials       75       75           

Flag	Coverage Δ
unittests	62.42% <67.56%> (+<0.01%)	⬆️

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