feat(seer): add the agent conversation embeds

[billyvg]

Adds two Seer markdown embeds for Explore > Agents:

• conversation — one AI agent conversation. Inline renders a link; block renders the transcript with its LLM call, token, cost and tool totals.
• conversationsQuery — the conversations list filtered by a search. Inline renders a link; block previews the first five matching rows with duration, message count, errors and cost.

Both are gated on organizations:gen-ai-conversations, which already exists in temporary.py, so neither reaches the agent until an org has it.

The last of four independent branches adding single-resource Seer embeds — see also #123901 (profile), #123905 (event) and #123906 (log). They all touch schemas.ts, index.ts, the stories page and the generated widget JSON, so whichever merges first leaves the rest needing a rebase plus a pnpm gen:embed-widgets re-run.

Notes for review

Both blocks avoid the route-level machinery, because it is URL-coupled and an embed must not touch the host page's history (embeds/README.md):

• The list block builds its own query rather than using useConversations, which takes no arguments and reads cursor/filters through nuqs.
• The transcript composes MessagesPanel + ConversationAggregatesBar directly rather than ConversationViewContent, which writes its tab and detail-tab state back to the URL. Message selection is local useState, with a test asserting the router never changes.

Two shape details worth a look:

• Content flattening. useConversations normalizes firstInput/lastOutput before handing rows out, but the raw endpoint returns string | {type, text}[] | null. Since the block calls the endpoint directly, it flattens them itself, then strips markdown to a single line for the cell.
• The agent filter lives in two places. The list view keeps it in its own agent URL param and folds it into the span query only when calling the API. The link mirrors the former, the block the latter, so both are filtered identically.

Ordering also differs: the endpoint returns by relevance, and the list view sorts newest-first before rendering, so the preview re-sorts to match.

Testing

10 tests across both embeds — inline hrefs and their padded time windows, the transcript, aggregates, API-title-wins-over-tag-title, selection staying local, the error state, the row preview with ordering and formatting, content-part flattening, and the empty state. The whole seer/markdown suite passes; oxlint and oxfmt are clean, and pnpm gen:embed-widgets produces no diff.

🤖 Generated with Claude Code

https://claude.ai/code/session_016YUmhMZLo8geXJa93daPEQ

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[github-actions]

Story previews

Preview the stories changed in this PR on the Vercel deployment:

• app/components/seer/markdown/seerMarkdown.mdx

_{Preview deployment: https://sentry-6texhaknz.sentry.dev}