fix: respect custom storage path for global custom modes

[roomote]

This PR addresses Issue #8122 where custom storage paths were not being respected when resolving global custom modes files.

Problem

When a custom storage path is configured via roo-cline.customStoragePath, the extension was still looking for global custom modes in the default location instead of the configured path.

Root Cause

The ensureSettingsDirectoryExists() function was building the settings path directly from context.globalStorageUri.fsPath + "settings", bypassing the custom storage logic in getSettingsDirectoryPath().

Solution

Updated ensureSettingsDirectoryExists() to delegate to getSettingsDirectoryPath(), which properly honors the roo-cline.customStoragePath setting.

Changes

• src/utils/globalContext.ts: Updated ensureSettingsDirectoryExists() to use getSettingsDirectoryPath()
• src/core/prompts/instructions/create-mode.ts: Updated to use getSettingsDirectoryPath() for displaying correct path in help text
• src/utils/migrateSettings.ts: Updated to use getSettingsDirectoryPath() for consistent custom path handling

Impact

With this fix, when roo-cline.customStoragePath is set to /Users/SOMEBODY/.roo:

• Global modes will be correctly read/written at /Users/SOMEBODY/.roo/settings/custom_modes.yaml
• Global MCP settings will be at /Users/SOMEBODY/.roo/settings/mcp_settings.json
• Project-local .roomodes behavior remains unchanged

Testing

• All existing tests pass
• Manual testing recommended with custom storage path configuration

Acceptance Criteria (from issue)

1. Set roo-cline.customStoragePath to an absolute path
2. Place a valid custom_modes.yaml at <customPath>/settings/custom_modes.yaml
3. Verify Modes UI displays those modes and updates persist to the same file

Fixes #8122

Thanks to @hannesrudolph for the excellent bug analysis and suggested fix!

---

Important

Fixes issue where custom storage paths were ignored for global custom modes by updating path handling functions to use getSettingsDirectoryPath().

• Behavior:
  • Fixes issue where roo-cline.customStoragePath was ignored for global custom modes.
  • Updates ensureSettingsDirectoryExists() in globalContext.ts to use getSettingsDirectoryPath().
  • Updates createModeInstructions() in create-mode.ts to use getSettingsDirectoryPath() for correct path display.
  • Updates migrateSettings() in migrateSettings.ts to use getSettingsDirectoryPath() for consistent path handling.
• Impact:
  • Global modes and settings are now correctly read/written to the custom path if roo-cline.customStoragePath is set.
  • Project-local .roomodes behavior remains unchanged.
• Testing:
  • All existing tests pass.
  • Manual testing recommended with custom storage path configuration.

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[roomote]

Reviewing my own code is like debugging in a mirror - everything looks backwards but the bugs are still mine.

The fix correctly addresses the issue by ensuring ensureSettingsDirectoryExists() honors the custom storage path. However, I found another location (src/core/prompts/sections/modes.ts line 10) that still directly builds the settings path - though it's not part of this PR, it should probably be updated in a follow-up to maintain consistency.

[roomote]

Is this comment necessary? The implementation is clear enough that getSettingsDirectoryPath handles directory creation. The comment might become outdated if the implementation changes.