v0.2.6 — Mindmap click no longer hijacks expand

Patch on top of v0.2.5.

What

Plain click on a mindmap node was eaten by our chat-prompt handler instead of triggering markmap's native expand/collapse. The user saw the node text flicker (both handlers racing) and the click silently sent the node to chat instead of expanding the subtree.

Fix

Gate the chat-send on Shift+Click:

Gesture	v0.2.5	v0.2.6
Click	Sends node to chat (and tree flickers)	Expand/collapse subtree (markmap default)
Shift+click	n/a	Send node to chat

The Shift+Click path uses capture-phase + `stopPropagation()` so when the user explicitly asks for chat-send, markmap doesn't also toggle the node underneath them.

Hint copy updated to "Click to expand · Shift+click to explore in chat".

Plus a small token-cleanup pass on the same file (the earlier sweep left `bg-indigo-100 dark:bg-accent-soft0/20` — a typo with a stray trailing `0`).

Commits

```
$(git log -1 --format=%h) fix(ui): mindmap node click hijacked expand/collapse — bump 0.2.6
```

Full diff: v0.2.5...v0.2.6