feat: add save/revert functionality and improve file modification tracking

[vgcman16]

Add save/revert functionality and improve file modification tracking
Changes
Added save/revert functionality:

Save button to persist file changes
Revert button to restore original content
Buttons only appear for modified files
Fixed file modification tracking:

Files no longer show orange indicator during initial creation
Orange indicator only appears after first modification of existing file
Improved sync between stores for consistent modification state
Technical Details
Modified files.ts to properly track new vs existing files
Updated workbench.ts to check file state before marking as modified
Updated editor.ts to handle save/revert operations
Simplified action-runner.ts to delegate modification tracking to files.ts
Added version history tracking for better file state management
Testing
Create new file: No orange indicator
Modify existing file: Shows orange indicator
Save changes: Persists modifications
Revert changes: Restores original content

[hillct]

This is really great work. I wonder though if nanostores is a bit too low level and versioning this way might represent a maintainability challenge on a going forward basis, relative to something like https://github.com/isomorphic-git/isomorphic-git

I'm throwing this into the mix not because I have time to implement this and see if it is in some way better/worse a solution, but just to get @vgcman16's thoughts on why one approach is superior to the other.

Areas of consideration:

• Dependency project upkeep and documentation (nanostores vs isomorphic-git)
• Convenience of future remote integrations (push a git repo, for example)
• Robustness & maintainability of local versioning functionality
• Duplication of effort

To be clear, these are meant to potentially be arguably construed in support of either approach.