T39c Theme · Platform passes review

AGENTS.md

@@ -186,6 +186,7 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - `typography::Ellipsis` shapes its line with the text style's own run, so a strike or an underline set on its box shows (`lists::ListItem::struck`, a closed task's title).
 - Focus that must follow an item to another parent is taken by the owner and keyed by the item: a handle gpui makes for an element dies with its path (`project::KanbanBoard`, whose cards keep focus across columns).
 - The theme's `platform`, the system's to start, decides the window buttons Ely draws, the title bar's layout and key caps, `secondary` included (`typography::keys::keystroke`). A title bar whose buttons the OS draws follows the OS.
+- A centered title sits between a start and an end that grow alike from a zero basis, their padding on a box inside them, since taffy counts padding in the flex base; their content is their least width, so the title gives way before either end (`shell::TitleBar`).
 - A pane the window's blur shows through is `shell::Vibrancy`, filled with the palette's `glass`, in a window opened `WindowBackgroundAppearance::Blurred`: vibrancy on macOS, acrylic on Windows. gpui 0.2.2 has no Mica.
 - The chart's hues go by `theme::HUE_NAMES`, for an event's color and a label's alike.
 - Text whose every character counts, encoded data and keys, goes through `typography::literal`: JetBrains Mono draws `==` and `->` as ligatures (`devtools::Encoder`).

TASKS.md

@@ -134,7 +134,7 @@ Per-component lines live in `tasks/`. Tags there:
 - [x] T38b Interaction · Keys, scroll and focus — `tasks/ch31-43.md`
 - [x] T39a Theme · Editing — `tasks/ch31-43.md`
 - [x] T39b Theme · Importing — `tasks/ch31-43.md`
-- [ ] T39c Theme · Platform
+- [x] T39c Theme · Platform — `tasks/ch31-43.md`
 - [ ] T40 i18n & a11y
 - [ ] T41 Maps
 - [ ] T42 Misc
@@ -426,3 +426,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T39b | 2 | PASS | |
 | T39c | 1 | FAIL | Windows caption buttons took their row's height; a long Windows title pushed the buttons past the bar |
 | T39c | 2 | FAIL | an untitled Windows bar lost its spacer; a centered title ran under the Linux buttons; caption buttons ignored the window's rem |
+| T39c | 3 | PASS | |