Why This Matters

the publish node is currently doing rendering, ingest, Slack, Discord, Telegram, and GitLab MR note posting all in one file.

Read First

• app/nodes/publish_findings/node.py
• app/integrations/gitlab.py

Scope

1. Extract the GitLab MR write-back branch into one helper module under the publish_findings package or a delivery utility module.
2. Move _build_mr_note() with it unless a better home is obvious.
3. Keep the GITLAB_MR_WRITEBACK env-flag behavior unchanged.

Tests / Coverage

• relocate the existing GitLab note tests into tests/nodes/publish_findings/
• add one test for env flag off
• add one test for MR IID missing
• add one test for write-back failure not crashing the report flow

Acceptance Criteria

• the publish node calls a small GitLab helper instead of inlining the branch
• behavior and env gating remain unchanged
• the helper has direct tests