Refactor task history persistence to use file-based storage

[KJ7LNW]

Context

The current task history persistence mechanism stores all history items directly in VSCode's globalState, which is causing several critical issues:

1. VSCode Warnings: The extension triggers VSCode warnings about excessive globalState usage:

   WARN [mainThreadStorage] large extension state detected (extensionId: RooVeterinaryInc.roo-cline, global: true): 6173.2822265625kb. Consider to use 'storageUri' or 'globalStorageUri' to store this data on disk instead.
   

2. Extension Crashes and UI Issues: Users experience various issues that may be related to memory management and globalState limitations:

   • Complete extension crashes or grey/white screens
   • Memory leaks consuming all available RAM
   • Possible globalState race conditions between VS Code instances leading to hangs, crashes, and VS Code instability

3. Performance Degradation: Even before crashing, the extension suffers from performance issues due to loading and processing large amounts of history data at once.

4. Scale Problem: A busy developer can accumulate tens of thousands of tasks over the course of a year. At this scale, the globalState approach becomes completely unsustainable.

Implementation

This PR implements a new architecture for task history persistence:

1. File-based Storage System:

   • Store individual history items as JSON files in a directory structure organized by year and month (task_history/YYYY/MM/)
   • Use globalState only for monthly indexes to enable efficient lookups
   • Implement safeWriteJson utility for data integrity during file writes

2. Frontend Changes:

   • Modify ClineProvider to provide availableHistoryMonths list instead of full taskHistory
   • Update frontend to fetch history data month-by-month based on available months
   • Add loading indicators and empty state handling in history view

3. Migration Process:

   • Automatically migrate existing taskHistory data from globalState to the new file-based system
   • Create a backup of the old data before migration

How to Test

1. Install the extension and verify that existing history is migrated correctly
2. Create new tasks and verify they are saved properly
3. View history and verify it loads correctly
4. Check that large history sets no longer cause VSCode warnings or crashes

Get in Touch

Discord: KJ7LNW

Fixes: #3784

[KJ7LNW]

@cte @mrubens @hannesrudolph

This is a first pass to fix the growing bloat from task history that is stored in the global extension state. It assumes that #3772 has been merged for JSON safety.

The biggest point for review is that it converts existing global state task history into on-disk JSON structures. It converts my global state of 2800+ historical tasks quiet nicely, and I have verified the file output and all existing tasks and search functionality appears to function. Creating new tasks or modifying existing ones adds to the new JSON files and everything seems to proceed as expected.

There are still some optimizations to do:

1. history preview does not need to load all task history, as only 3 items are shown on the front page, so that will substantially speed up extension load time
2. the entire task list could theoretically load tasks in chunks by month, and then automatically load more as you scroll down, but I am not sure if I want to add that in an initial commit because it is complicated for things like searching that expect everything to be loaded. For now, it just loads all tasks into the task history interface (which is the same behavior as before)
3. there would probably be a first load spinner indicating conversion progress. My system it converts so fast I do not notice the difference but people who may have tens of thousands of boomerang tasks might notice.

This is an intentional break from backwards compatibility specifically for task history storage, however the old global state is not deleted, so if you downgrade to an older version (or if you are a developer testing things prior to this PR), you will still have everything that you used to have.