Renames `RightPanelTab::Changes` to `Scm` in place. `#[serde(rename =
"changes")]` works in both directions, so what lands on disk is unchanged
and a build from before this commit reads the config back without kicking
anyone off the panel they left open — a fourth variant could not do that,
and 260px has no room for a fourth tab tile anyway. The action name
`ShowRightPanelChanges` stays put because `Config::keybindings` is keyed by
it, and every existing custom binding would otherwise be orphaned.
The panel body moves to `src/ui/scm/panel.rs` byte for byte; it still
renders the flat `git diff HEAD` list. Alongside it the module gets the
pieces the rest of the feature is built from: the shared status glyph and
colour tables (one definition instead of three that drift), the path and
timestamp helpers a 260px column needs, and the panel's state types.
Also wires the whole surface: fourteen actions, their key bindings, ten
palette commands in a `Git` group of their own, and the translations.
`ScmCommit` takes `secondary-enter`, which macOS already gives
`ToggleFullscreen`; the two coexist because the commit binding is scoped
to the commit box, and `every_default_chord_is_claimed_by_exactly_one_action`
now checks uniqueness per context instead of globally, which is the actual
invariant gpui enforces.
`Config` gains `diff_view` and `scm_graph_expanded`. Both default to what
happens today.
Two new icons. `git-sync.svg` is deliberately not `refresh.svg`: the panel
header already carries a refresh tile, and the same glyph meaning two
different things one row apart reads as a bug.
Adds `every_action_has_a_binding_arm`, which walks every action in
`default_bindings` rather than only the ones shipping a default keystroke.
The gap it closes is an action listed in Settings with no `make_binding`
arm behind it: the user assigns a key and the key silently does nothing.
