docs(client-web): sync the web card contracts to the scrolling source list

The READMEs of ui-primitives and ui-conversation still documented the
removed maxSources prop, DEFAULT_WEB_MAX_SOURCES, CHAT_WEB_MAX_SOURCES,
and the head/tail collapse; the 2026-07-30 frontend note described the
same as current behavior. Restate all of them as the fixed-height scroll
container and cross-link the two notes both ways.

Bound the model-visible/card-visible correspondence: spill-policy's
tools/post-execute replaces an oversized result's content while leaving
presentationMeta whole, so the card's contract is the view it receives,
not the model's context.

Narrow the unit test's name and header comment to what jsdom establishes
(one <ol>, no expand control); jsdom does not resolve CSS Modules layout,
so the scroll geometry belongs to an assembled browser case.

packages/client/ui-primitives/README.md

@@ -30,7 +30,7 @@ Pure React atoms (zero cordis): StateDot, ic_ds_* icons, Button/Pill/Menu/Modal/
 
 ## Web retrieval
 
-`WebBlock` renders a completed web retrieval, one component for both kinds of the `web` render intent (discriminated by `kind`). A `search` shows an optional provider answer (through `MarkdownText`) above an ordered citation list: each source is a safe external link labelled by its title, or its hostname, falling back to the raw URL when the URL does not parse or has no hostname (a `file:`/`data:` URL) so a label is never blank; its snippet and publication date render below it. Only http(s) URLs become anchors (`target`/`rel` set) — the http(s) subset of the allowlist `MarkdownText` applies to untrusted links (it also permits `mailto:`, excluded here); any other URL renders as plain text. A long list caps at `maxSources` (default 16, the TerminalBlock split arithmetic) with a head/tail collapse; the collapsed tail keeps each source's original citation number via `<li value>`, and the expand control is a marker-less `<li>` so the `<ol>` stays valid HTML. When a search legitimately returns no answer and no sources, the card shows an explicit empty-state note rather than a blank `<ol>` (the chat row does not surface the raw result content). A `fetch` shows a compact summary: the linked final URL and its HTTP status. Both mark a capped retrieval. Rationale: [the web result card note](../../../.agents/notes/implemented/feature/2026-07-30-web-result-card-frontend.md).
+`WebBlock` renders a completed web retrieval, one component for both kinds of the `web` render intent (discriminated by `kind`). A `search` shows an optional provider answer (through `MarkdownText`) above an ordered citation list: each source is a safe external link labelled by its title, or its hostname, falling back to the raw URL when the URL does not parse or has no hostname (a `file:`/`data:` URL) so a label is never blank; its snippet and publication date render below it. Only http(s) URLs become anchors (`target`/`rel` set) — the http(s) subset of the allowlist `MarkdownText` applies to untrusted links (it also permits `mailto:`, excluded here); any other URL renders as plain text. The whole list renders in one fixed-height scroll container (`max-height: 320px`, `overflow-y: auto`), so a list taller than that scrolls vertically in place instead of growing the card; `<li value>` pins each source's citation number, contiguous from 1, rather than leaving it to the `<ol>`'s implicit count. When a search legitimately returns no answer and no sources, the card shows an explicit empty-state note rather than a blank `<ol>` (the chat row does not surface the raw result content). A `fetch` shows a compact summary: the linked final URL and its HTTP status. Both mark a capped retrieval. Rationale: [the web result card note](../../../.agents/notes/implemented/feature/2026-07-30-web-result-card-frontend.md) and [the source scroll note](../../../.agents/notes/implemented/feature/2026-08-03-web-search-source-scroll.md).
 
 ## Model Experience
 
@@ -45,5 +45,5 @@ None; this package neither assembles nor sends a provider request.
 - **Glyph-level icons are redrawn approximations** — the fish logo (and the sparkle held by ui-conversation) come from font glyphs whose vector geometry is not exportable from the local design data; hand-authored recreations stand in until an exact export path exists.
 - **Pill and Input have no design source** — both atoms are self-defined; the sidebar search field and view-tab strip that resemble them are consumer-owned compositions, not these atoms.
 - **StateDot `Active` variant is a hidden placeholder in the design** — not implemented; the four shipped states (done/warning/ongoing/error) are the complete P-I surface.
-- **User-facing copy localizes through label props, defaulting to the original Chinese literals** — the atoms are zero-cordis and cannot reach `ctx.locale`, so `HoverCard` (`copyLabel`/`copiedLabel`), `TerminalBlock` (`labels`), `JsonTree` (`labels`), `CodeBlock` (`copyLabel`/`copiedLabel`), `MarkdownText` (`codeLabels`), `JsonBlock` (`truncatedLabel`), `ConnectionBanner` (`label`), and `Modal` (`closeLabel`) take their copy as optional props with the previous hardcoded strings as defaults. Localized plugins pass dictionary-driven labels from their own `t` seat; a consumer that passes nothing renders exactly the pre-localization output. `WebBlock` does not yet follow this pattern: its source expand/collapse controls, source-list and fetch truncation notes, and empty-search note stay inline Chinese, pending the same label-prop treatment.
+- **User-facing copy localizes through label props, defaulting to the original Chinese literals** — the atoms are zero-cordis and cannot reach `ctx.locale`, so `HoverCard` (`copyLabel`/`copiedLabel`), `TerminalBlock` (`labels`), `JsonTree` (`labels`), `CodeBlock` (`copyLabel`/`copiedLabel`), `MarkdownText` (`codeLabels`), `JsonBlock` (`truncatedLabel`), `ConnectionBanner` (`label`), and `Modal` (`closeLabel`) take their copy as optional props with the previous hardcoded strings as defaults. Localized plugins pass dictionary-driven labels from their own `t` seat; a consumer that passes nothing renders exactly the pre-localization output. `WebBlock` does not yet follow this pattern: its source-list and fetch truncation notes and its empty-search note stay inline Chinese, pending the same label-prop treatment.
 - **`TerminalBlock` is not a terminal emulator** — it renders settled or still-running command output, not an interactive session: SGR color and attributes are honored, and so are the in-line cursor movements a progress line uses — carriage return, backspace, erase-in-line, tab stops and character width. Absolute cursor positioning, screen clearing, and alternate-screen sequences are stripped. Basic-16 magenta and cyan have no token equivalent and stay literal rgb.