fix: support Antigravity 2.0.1 IDE and Agent Manager split architecture

[Izhan-07]

Description

What does this PR do?
This PR fixes profile isolation for the recent Google Antigravity 2.0.1 update.

Google recently introduced a major architectural change that bifurcates the platform into two separate applications with their own data directories:

1. The Agent Manager (which retained the old Antigravity.exe and .antigravity data folder).
2. The IDE Editor (which now uses a new Antigravity IDE.exe and .antigravity-ide data folder).

Because of this split, multigravity-pro was only isolating the Agent Manager state, causing the IDE extensions and settings to bleed across profiles or fail to load. This PR updates the directory scaffolding and launch logic to fully support the new bifurcated environment while maintaining backward compatibility with older installations.

Specific Changes in multigravity.ps1:

• Find-Antigravity: Updated the executable search paths to prioritize the new "Antigravity IDE.exe", while retaining the legacy "Antigravity.exe" paths as a fallback for older versions.
• Invoke-CreateProfile: Added directory generation for .antigravity-ide\extensions alongside the existing .antigravity scaffolding so the new IDE can operate in full isolation.
• Invoke-CreateAuthOnlyProfile: Added parallel symlink logic to ensure the new .antigravity-ide\extensions directory is properly linked to the system's global IDE extensions when using the --auth-only flag.
• Invoke-ProfileStats: Updated the extension path counter to read from the new IDE directory so terminal stats accurately reflect installed extensions.

Testing:

• Tested locally on Windows 11.
• Verified that creating a new standard profile properly isolates the IDE environment.
• Verified that launching an --auth-only profile successfully shares global extensions but isolates the account state.