Rename 'directory' command to 'workspace' and unify terminology

[keithguerin]

Following the UX decision to use 'Workspace' as the standard term for the environment (CWD + trusted directories), we need to:

1. Add '/workspace' as an alias for '/directory' (or rename it).
2. Update all UI strings in directoryCommand.tsx to use 'Workspace' terminology.
3. Update MCP command messages to use 'workspace' scope instead of 'project'.
4. Standardize setting labels (e.g., 'Hide CWD' -> 'Hide Workspace Path') and descriptions.
5. Once complete, remove the temporary '(/directory)' hint from the footer.

Current footer label: 'Workspace (/directory)'

[ravencore06]

/assign

[gemini-cli]

👋 @ravencore06, thanks for your interest in this issue! We're reserving self-assignment for issues that have been marked with the help wanted label. Feel free to check out our list of issues that need attention.

[keithguerin]

Created PR #20740 to address this. Per Core/UX chat on 2/18.