feat(slack): refetch unfurl attachments for inbound messages with URLs

[sentry-junior]

Fixes #416

Problem

Slack generates link unfurl previews asynchronously. The initial message event arrives with an empty attachments array; the actual unfurl data lands later via a message_changed event. The existing message_changed handler only fires for newly-added bot mentions, so unfurl data was silently dropped and Junior never saw it — even when the preview was visible in the Slack UI.

Fix

Add maybeRefetchSlackUnfurlAttachments (slack/unfurl-fetch.ts) called in reply-executor.ts before prepareTurnState finalises the user turn text.

When the inbound message.raw has no attachment data and the text contains a URL, the helper retries conversations.replies with short delays (400 ms → 800 ms → 1.3 s). On a match, fetched attachments are merged back into the raw object so the existing appendSlackLegacyAttachmentText path renders them as normal [attachment] … lines. The call is a no-op for messages without URLs.

Verification

• 10 unit tests: skip-when-has-attachments, skip-when-no-URL, skip-when-missing-ids, enrich-on-first-retry, enrich-on-second-retry, fallback-when-all-retries-miss, fallback-on-API-error, threadTs-fallback, raw-fields-preserved.
• pnpm typecheck clean.

Action taken on behalf of Sergiy Dybskiy.

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Project	Deployment	Actions	Updated (UTC)
junior-docs	Ready	Preview, Comment	May 25, 2026 4:16pm

[dcramer]

I'm not really sure this is a good idea. Whats the issue? Having arbitrary "try to process the message again" delays is going to cause all sorts of problems.

[sergical]

@dcramer we have the gibpotato app that unfurls discord links and adds content as attachments.

for some reason even when the message preview before sending already includes the unfurled content preview of the attachments, junior fails to see them when posted.

beyond discord unfurl in our usecase, i feel like theres other usecases where this async attachment context might be helpful?

i could be wrong and this could be not the right solution to a problem (or not big enough of a problem to solve for)

Context thread on slack: https://sentry.slack.com/archives/C0B2KJG9B5Z/p1779722822970109