Add design folder and README

design/detail_window.md

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+# Detail Window Feature
+
+**Purpose**: Shows a single view (YAML, Describe, Logs, Shell) for a Kubernetes object.
+
+**Size**: Default 380×362 px, resizable via bottom‑right corner handle. Sibling windows in the same column/row resize proportionally.
+
+**Header (36 px)**:
+- Shape glyph (type‑specific colour) + view label (uppercase, accent colour).
+- Object name + status badge.
+- Close button (×).
+- `cursor: grab` – drag to reposition within the canvas.
+- Double‑click → maximize to fill available space (below top bar, above bottom bar, side margins 22 px). Press `z` or double‑click again to restore.
+
+**Tab Bar**: YAML · Describe · Logs · Shell. Shell tab disabled for non‑exec objects (opacity 0.45).
+
+**Content area**: `<pre>` with `overflow:auto; height:286px; font-family:'IBM Plex Mono'; font-size:12px; line-height:1.65`. Custom scrollbar (8 px, rgba(140,165,200,.18)).
+
+**Keyboard focus**:
+- Mouse‑over window + type → focuses that window’s content (shell input when a Shell view is active).
+- Global `keydown` capture routes keys to the hovered window if it is a shell.
+
+**Maximize (`z` key or double‑click header)**:
+- Resize to `width = viewport.width - 44px`, `height = viewport.height - topBarHeight(68px) - bottomBarHeight(66px)`.
+- Set camera so the window fills the viewport (`zoom = 1`).
+
+**Secret YAML auto‑decode**: When rendering a Secret, base64‑decode all `data` values and display plaintext with a banner `⊙ secret values auto‑decoded`.