fix(flow): preserve comment anchor in getUserData

[baokimho]

Summary

Fixes #1186.

getUserData sends a prompt, but comment-triggered private-reply flows did not treat it as a message-producing step. As a result, the commentAnchor was not passed into getUserData, and the prompt enqueue path also dropped the anchor.

This PR keeps the fix scoped to #1186:

• adds getUserData to MESSAGE_PRODUCING_STEP_TYPES
• forwards commentAnchor through enqueueFlowStepMessage
• updates the related invariant/docblock
• adds regression coverage for both unspent and spent anchor cases

Behavior

This now ensures that:

• a question-first getUserData can use the unspent comment anchor
• a getUserData after another message-producing step receives the spent anchor
• normal non-comment flows remain unchanged

Validation

• Comment-triggered private reply: getUserData never receives the commentAnchor — a question-first flow never claims the anchored DM, and a question after a sendText bypasses assertCommentPrivateReplyFollowUpDeliverable #1186 regression tests: 5/5 passed
• neighboring worker tests: 155/155 passed
• Instagram tests: 55/55 passed
• Messenger tests: 55/55 passed
• worker TypeScript check: passed
• git diff --check: passed

Biome still reports formatting findings on the touched files, but the parent revision reports the same findings unchanged, so this is a pre-existing baseline issue.

[Copilot]

🟡 Changes recommended

The Messenger date/datetime prompt path still drops commentAnchor and needs propagation plus regression coverage.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

This PR fixes comment-anchor propagation for getUserData in comment-triggered flows.

Changes:

• Treats getUserData as message-producing.
• Forwards anchors through text prompt jobs.
• Adds anchor lifecycle and regression tests.

A moderate review finding remains: Messenger date/datetime prompts use a direct chat-message path that drops commentAnchor.

File summaries

File	Summary
apps/worker/src/integration/handlers/get-user-data.ts	Forwards anchors for text prompts.
apps/worker/src/integration/handlers/flow-utils.ts	Registers getUserData as message-producing; the date/datetime path still needs anchor propagation.
apps/worker/__tests__/get-user-data.test.ts	Tests prompt anchor forwarding.
apps/worker/__tests__/flow.test.ts	Tests anchor lifecycle behavior.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Lite

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