put the previewed browser tab in the url

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/navigation-audit.md

@@ -39,7 +39,8 @@ That fix is the template for the HIGH items below. **Caveat:** the fix only did
 was in this list; the Projects feature was removed end to end on 2026-07-30, so the route is gone with it. H3
 and navigate-site 22 below still name it — they are the record of work that happened, not of code that exists.)
 **Flat screens:** `/` `/files` `/music` `/tasks` `/skills` `/processes` `/activity`
-`/system-monitor` `/task-logs` `/plans` `/terminal` `/desktop` `/browser` `/code-editor`.
+`/system-monitor` `/task-logs` `/plans` `/terminal` `/desktop` `/code-editor`. (`/browser` is a pair now too —
+`/browser/:tabId`.)
 The five settings pages are route **pairs** now, not flat screens — `/settings/{profile,ai,system,integrations,user-management}`
 plus a `:section` each (M6). There has never been a `/settings/apps`; that entry was wrong when this list
 was written.
@@ -101,7 +102,15 @@ is **one design decision** that cascades across many files:
 
 - **Dock / Header active styling** (`Dock.tsx:43,78` · `Header.tsx:53,112`) — destinations are already real
   `<Link>`s; only the *active* class is JS-derived from `useLocation`. Switch to react-router `<NavLink>` and drop the hand-rolled `isActive`.
-- **Browser tabs** (`Browser/TabList.tsx:93`) — ephemeral CDP targets (polled, come/go every few seconds); a durable `/browser/:targetId` is dubious. Probably leave as selection.
+- ~~**Browser tabs**~~ (`Browser/TabList.tsx:93`) — **done, against this file's own advice.** The objection
+  was that a CDP target id is ephemeral, so a durable `/browser/:tabId` is dubious. True of *bookmarking*,
+  and irrelevant to everything else the URL buys: the id was in an onClick closure, three components read a
+  `BROWSER_SELECTED_TAB` global, and the row could not be cmd-clicked. Staleness is handled where it
+  actually shows up — the preview now distinguishes "no tab open" from "that tab is no longer attached"
+  by checking the polled target list, which it gets from the same React Query key the list uses, so it
+  costs no extra request. En route: the row's Focus and Close buttons were nested *inside* the row
+  `<button>`, which is invalid HTML and only worked because of two `stopPropagation` calls; they are
+  siblings of the anchor now. And its "Set up in Integrations" was a raw `<a href>` that reloaded the SPA.
 - **Jobs step/iteration** (`Jobs/JobDetail.tsx:234,255`) — intra-detail sub-selection; only if we want `/jobs/:id/:stepKey` deep links.
 - **Preview slug** (`Preview/PreviewApp.tsx:23`) — Preview usually derives its target from the surrounding dashboard/project `cwd`; the manual picker is a fallback. Probably leave URL-less.
 - **FileBrowser widget** (`FileBrowserWidget/.../BrowseTab.tsx:36`) — compact sidebar widget; keeping its browse cursor local is defensible.
@@ -209,7 +218,7 @@ publishers means changing the chat panel, which is another agent's, so it is wri
 - [ ] Dock + Header + mobile sheet → react-router `<NavLink>` for active state; drop hand-rolled `isActive` (`Dock.tsx`, `Header.tsx`).
 - [ ] "New Chat" → `<Link to="/chat/new">` (`SessionList.tsx:68`) once H4's channel cleanup lands.
 - [ ] Jobs back button + any `navigate('/jobs')` → shared `BackButton` (`JobDetail.tsx:709`).
-- [ ] Decide/skip: Browser tabs, Jobs step deep-link, Preview slug, FileBrowser widget, Music-favorites/Monitor-scope view toggles.
+- [ ] Decide/skip: Jobs step deep-link, Preview slug, FileBrowser widget, Music-favorites view toggle. (Browser tabs: **done** — see the LOW section. Monitor scope: **done** as M10, it was not a view toggle.)
 
 ### Cross-cutting for the refactor itself
 - [ ] Standardise a URL-as-source-of-truth pattern for panel selection (replace the `usePanelChannel`/`useGlobal`