feat(chat): view context — tell the assistant what you're looking at

An eye next to the paperclip shares what the user has open with their next
message: the page, the folder being browsed, the file open in the viewer and
any highlighted passage (line numbers where a source view exists), plus which
entity a detail page is about. The bag is client-authored {label, value} pairs
in English — the backend only clamps (chars, never bytes), neutralizes the
harness tag and renders one <system-extra> block per message, deduped
consecutively so it appears exactly when the view changed. On by default,
per-device toggle, hover/tap to preview, a chip on every sent message;
docs/view-context.md for users, an updated harness.md clause for the model.

CHANGELOG.md

@@ -16,6 +16,20 @@ release PR may merge — and a section is closed at the commit that bumps it.
   or delete wherever you have write access; the read-only places say so. Your memory
   notes are readable here for the first time (changing them still goes through the
   assistant).
+- The assistant can be told what you are looking at: the eye next to the paperclip sends
+  what you have open along with your next message, so "what is this?" needs no explaining.
+  It names the page you are on; the folder you are browsing in Files or in a project; the
+  file open in the viewer and any passage you highlighted in it — line numbers included
+  where you are looking at the source — so "what is in here?" and "rewrite this sentence"
+  work without naming anything; and, on a detail page, which project (and which of its
+  tabs), member, connector, plugin, conversation, tool call or LLM request you opened.
+  The active section follows you in Tasks, Models, Background agents, the Marketplace
+  search and the mobile app. Like an attachment, what the eye sends goes to the AI
+  provider together with your message — hover it (or tap it) to read exactly what would
+  go out, click it to stop sharing; the choice is remembered on this device, and every
+  message shows a chip with what it carried. Very long highlights are trimmed, with a
+  note saying how much was left out — the assistant can still read the whole file itself.
+  On by default.
 - Several conversations per source: open extra chats with `+`, and the tab bar you left
   open is restored at your next login, on any device.
 - A background task now reports back into the chat that started it instead of only the
@@ -68,6 +82,8 @@ release PR may merge — and a section is closed at the commit that bumps it.
 - The re-login dialog no longer hijacks the login screen, the new-chat `+` menu is visible
   and clickable, and the session-detail page stays live instead of freezing on a snapshot.
 - A silently dead agent WebSocket is detected and redialled.
+- Opening Files, Plugins, Shared folders or a plugin's own page from a link no longer
+  covers it with the full-screen chat: the chat docks to the side, as on every other page.
 - A generated image lands in your own workspace instead of a server folder nobody could
   reach, so the assistant can finally send it to you on Telegram, open it in the viewer,
   or work on it with a command. It still shows inline in the web chat, its file is named