fix(web-cards): restore AT status text, guard file-link keys, add read docs

Address review of the ToolRow card refactor:
- ToolRow renders a visually-hidden run-state label (row.running/failed/stopped
  locale keys) so a running/failed/interrupted row is not a colour-only signal;
  the StateDot and the sweep are both aria-hidden. Restores the stopped-state
  text assertion in diff-card.spec at the ToolRow layer.
- The file-link button stops Enter/Space from bubbling to DisclosureRow's
  whole-row keydown, which would preventDefault the key and toggle expand
  instead of opening the file (the keyboard analogue of the click stopPropagation).
- search-row passes output={model.output} unconditionally, matching the other
  three card rows (ToolRow renders the card over the output when present).
- Assert locale: 'conversation' in the search/web/diff registration tests.
- Add the read render-intent paragraph to the ui-conversation README and a
  ReadBlock atom entry + Read section to ui-primitives (both languages).
- Update the grep fixture sample lines to the post-refactor SearchRow shape.
Refresh the code-mode-round, steering, and search-card goldens for the added
status text and updated sample lines.

packages/client/ui-conversation/README.md

@@ -18,6 +18,8 @@ A tool call declaring the `terminal` render intent renders its command output in
 
 A tool call declaring the `web` render intent renders its web retrieval inline, at both conversation render sites, through ui-primitives' `WebBlock`. `contract/web-card-model.ts` is the single derivation from the snapshot's `resultView`, mirroring the terminal card, so the sites cannot disagree about what a web call shows; it yields null — the generic path — for a running call, a non-web result view, a generic result view, a `card` tag this client version does not know, or a web card whose `kind` this client version does not know (a newer host's value, which the wire cannot be trusted to be `search` or `fetch`). The keyed `WebRow` registers one component under both `web_search` and `web_fetch`, discriminating on the tool name only for its icon and title; it composes the shared `ToolRow`, feeding the card as ToolRow's `web` body, so the retrieval is the row's collapsed-by-default expanded card (the same unified expand every card row has). A web-declaring tool without a keyed row lands on the `GenericToolCard` fallback, which routes the card through ToolRow the same way, and the details panel renders it at the primitive's full source allowance and, below the card, the flattened model-visible result content — a fetch body is readable only there, since its card carries only the URL and status. Rows cap at `CHAT_WEB_MAX_SOURCES` (8) against the panel's 16, the same summary-versus-reading split the terminal card draws ([decision](../../../.agents/notes/implemented/feature/2026-07-30-web-result-card-frontend.md)).
 
+A `read` call declaring the `read` render intent renders the returned file window inline, at both conversation render sites, through ui-primitives' `ReadBlock` — the line-numbered, syntax-highlighted content the tool projects. `contract/read-card-model.ts` is the single derivation from the snapshot's `resultView`; the read card is result-side only (a call carries no file content until `execute` returns), so a running read shows its summary alone and it yields null — the generic path — for a non-read result view or a `card` tag this client version does not know. The keyed `ReadRow` composes the shared `ToolRow`, feeding the card as ToolRow's `read` body, so it is the row's collapsed-by-default expanded card; the summary stays a path link that opens the file through the host. The render-site fallback and the details panel are read-aware too. Rows cap at `CHAT_READ_MAX_LINES` (8) against the panel's 16 ([decision](../../../.agents/notes/implemented/feature/2026-07-30-web-read-card-frontend.md)).
+
 A tool call declaring the `diff` render intent (the `write`/`edit` tools) renders its applied change inline through ui-primitives' `DiffBlock`, the same four-layer shape. `contract/diff-card-model.ts` is the single derivation from the `callView`/`resultView` pair; the settled result's hunks replace the call-time diff, and it yields null — the generic path — for any other card tag or a generic result view (write/edit's execution errors). The keyed `FileMutationRow` (registered under both `write` and `edit`) composes the shared `ToolRow`, feeding the diff as ToolRow's `diff` body, so it is the row's collapsed-by-default expanded card; the summary path link still opens the file through the host, and an errored mutation (no diff card) surfaces its error text through ToolRow's Output section with the first line in the collapsed summary. The render-site fallback and the details panel are diff-aware too. Rows cap at `CHAT_DIFF_MAX_LINES` (8) against the panel's 16 ([decision](../../../.agents/notes/implemented/feature/2026-07-30-web-diff-card.md)).
 
 The chat flow projects consecutive model-retry nodes across retry turns into one stable, muted status row updated to the latest attempt; every retry event remains in the runtime snapshot and session log. Its frontend countdown anchors the scheduled delay to client receipt, avoiding host/browser clock skew, rounds remaining time up to seconds, and has a one-second floor. The latest unresolved retry uses a left-to-right text shimmer. Subsequent turn facts distinguish an attempt that started from one cancelled during backoff, while the Host running bit only controls the live animation; the row then shows a static completed or cancelled label. Normal policy rows show the finite retry maximum; always policy rows show `∞`. Activating the row reveals the latest exact retry delay and failure message. The client runtime removes each failed step's streaming tail before its retry node arrives, while the status remains visible after a later attempt succeeds.