feat(ai-chat): show tool-call arguments in the action-log card (#392)

For tools without a friendly label (esp. external MCP tools like
Search_web_search) the card showed a generic "Ran tool <name>" with no
sense of what was searched. Add a compact one-line, dimmed summary of the
call's arguments under the label, pulled from part.input.

New pure toolInputSummary(part): picks the first present "primary" field
(query/q/searchQuery/url/urls/title/name/text/prompt), collapses
whitespace, clamps to ~140 chars; arrays render "first (+N)". It returns
undefined during input-streaming (the input grows while state is fixed and
messageSignature doesn't track input, so a live summary would freeze) —
the state flip to input-available re-renders the row with the final value,
so message-signature.ts is left untouched. The value renders ONLY through
Mantine <Text> (React-escaped) — no markdown/HTML, no XSS.

A showInput prop (default true) is threaded MessageList -> MessageItem
(+memo) -> ToolCallCard; the public share widget passes showInput={false}
so an anonymous reader never sees the agent's raw query text (mirrors
showCitations). No JSON fallback when no primary field is present.

closes #392

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/src/features/share/components/share-ai-widget.tsx

@@ -165,6 +165,9 @@ export default function ShareAiWidget({
             isStreaming={isStreaming}
             assistantName={assistantName}
             showCitations={false}
+            // Anonymous reader: suppress the tool-argument summary line so the
+            // agent's raw query/argument text isn't shown on the public share.
+            showInput={false}
             // Anonymous reader: neutralize internal/relative links in the
             // assistant's markdown so internal UUIDs/auth-gated routes don't
             // leak as clickable links (external http(s) links are kept).