Slack replies break markdown pipe tables

[sentry-junior]

Markdown pipe tables in assistant Slack replies render as broken/plain text instead of a compact table.

Example

• https://sentry.slack.com/archives/CDXAKMGTU/p1787752205237019?thread_ts=1787697915.428599&cid=CDXAKMGTU
• Reply used a comparison table (first-trace banner vs onboarding gate). In Slack it showed as broken row text rather than a table.

Verified

• Delivery runs model markdown through normalizeSlackReplyMarkdown → ensureBlockSpacing in packages/junior/src/chat/slack/mrkdwn.ts.
• ensureBlockSpacing inserts a blank line between consecutive non-empty non-list lines, and only keeps adjacent lines compact for list items.
• Pipe-table rows (| ... |) are not treated as a compact block, so a multi-row table becomes blank-line-separated rows before Slack delivery.
• Unit coverage in packages/junior/tests/unit/misc/output.test.ts exercises list/prose spacing, not markdown tables.

Unknown

• Whether Slack markdown_text / { type: "markdown" } would render contiguous pipe tables correctly if row adjacency were preserved, or whether tables need a different delivery shape entirely.

Requested by Matt Quinn.

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View Junior Session [Sentry]

[mjq]

jr's verbatim output in the Slack messsage:

| | first-trace banner | onboarding gate |

|---|---|---|

| source | polled detailed project API | ProjectsStore via useProjects() |

| updates live? | yes (5s poll until true) | only when store refreshes |