[ENHANCEMENT] Add "Current Editor Selection" context mention (selection only)

[hannesrudolph]

Type

Enhancement

Problem / Value

Selecting code and immediately prompting is a common flow. Today this is possible via a code action, but it's hidden and interrupts focus. Adding "Current Editor Selection" as a built-in context option would make prompting faster and more intuitive, aligning with expectations set by other tools.

Context

• Affects users who select text and then switch to Roo to prompt.
• Requested to only show this option when text is actually selected, to avoid confusion and cursor/caret visibility issues when focus changes.
• Users coming from Copilot expect the current editor/selection to be readily available without extra steps.

Desired behavior

• Provide a "Current Editor Selection" option in the context options so users can quickly include the currently selected text.
• Show this option only when there is an active text selection.
• Do not steal focus or cause the editor caret to disappear when switching to Roo.

Constraints/Preferences

• Keep the flow lightweight and unobtrusive.
• Handle unsaved edits so the included selection matches what the user sees.
• Avoid unnecessary context usage; include only what's selected.
• Consider a follow-up setting to auto-include the current editor file/selection by default for a frictionless experience.

[roomote]

I'm exploring a potential fix for adding the "Current Editor Selection" context option and will open a PR to share progress.