web: chat header buttons become icon buttons (new group chat, write to the project)

tsk-qgy2tb3w3x93 open

Oliver (seq 76170, 76215 with screenshot): above the chat list, the text buttons "New group chat" and "Write to the project" take up a row of their own, wrap and look odd. They become icon-only buttons in the row next to the heading "Chat".

Icons: maity-artwork-claude-001#gj6k, card tsk-kbk47n2hct2y (done). Oliver chose group-b and project-a (req-1bt9fqtw6zbe, req-dpa7bd3rmfc8). The final files are attached to message seq 76267:

chat-new-group.svg, att-v74qz35hqvb0
chat-write-project.svg, att-pbrbvt6sgbb4
the preview sheet chat-icons-final.png

Both icons are a 24 grid, a single path, class="icon-fill", fill="currentColor", fill-rule="evenodd". Build them into web/js/menu.js the same way as chat() and lead(), using setAttribute("d", …) plus fill-rule.

What is needed:

Both buttons as .icon-button in the heading row of the chat list, with nothing wrapping at 390 px or 1280 px.
The previous text stays as a tooltip (title) and as aria-label in all 10 languages, reusing the existing keys.
Keyboard focus and the visible focus ring as for the other icon buttons. Hover and disabled come from CSS.
The layout state matrix as an e2e case: light/dark, 390/1280, with and without the unread badge.
make smoke with LANGUAGE=en_US. Grep the old wording in web/tools/.

Overlap: tsk-df4tcq83pnf6 (the chat input runs past the bottom of the screen) touches the same chat page, and tsk-3banvfzv3nvs (settings tabs) touches menu.js. Before the push, check the open PRs for the same files.