feat: add vim-style gg/G navigation to sessions and projects views

[saurabh-hirani]

Problem

Session and project lists can get long — navigating item by item with j/k becomes tedious when the selection is far from the top or bottom.

Solution

Add vim-style gg (jump to first item) and G (jump to last item) keybindings to the Sessions and Projects list views. A lastKey field tracks the previous keypress to detect the gg sequence.

Testing

• gg jumps to the first item from any position
• G jumps to the last item
• Works on both Sessions and Projects tabs

Test layers

View-level tests (sessions_test.go, projects_test.go): Unit tests that verify SessionsView.Update() and ProjectsView.Update() correctly handle g/G keypresses in isolation. These test the view's internal key handling logic.

App-level tests (app_test.go): Integration tests that verify app.Update() actually routes g/G keypresses through to the views. These catch routing bugs that view-level tests cannot — for example, if app.Update() silently dropped g/G keys, the view-level tests would still pass but the feature would be broken in the binary. Both layers are necessary to ensure correctness at each level of the architecture.