M4 — Backend gap backlog #37129

Sub-issue of #37124.

Description

Draft the backend half of next quarter's context-gap backlog — explicitly deferred subsystem context (content lifecycle, caching, workflow, upgrade tasks), plus anything discovered during M0–M3 that's out of scope for this Rock. Draft by Oct 5; reviewed with the team (merged with Fabrizzio's testing/tooling half) by Oct 8.

Acceptance Criteria

• Backlog entry for content-lifecycle context (currently undocumented)
• Backlog entry for caching context (currently undocumented)
• Backlog entry for workflow-engine context (currently undocumented)
• Backlog entry for upgrade-task context (currently undocumented)
• Backlog entry for docs/integration/ — the directory exists (API_CONTRACTS.md is referenced by docs/core/SECURITY_PRINCIPLES.md:80), is unlinked from CLAUDE.md, and isn't owned by either Falcon or Scout in the current split — needs an ownership decision, not just a doc fix (discovered in M0, M0 — Backend context audit #37125). Resolved: both teams jointly own updating and keeping API_CONTRACTS.md correct. If a dev needs to update content covering endpoints clearly created by the other team, they must raise it and touch base with that team first to confirm the change makes sense before merging. Still open (mechanical, not a decision): linking it into CLAUDE.md's navigation index, and auditing its actual content against real source (never went through M1–M3's audit process).
• Each entry has a one-line problem statement and a rough size estimate (S/M/L), not just a title
• Backlog merged with Fabrizzio's half into one document
• Reviewed with the team and confirmed ready to become next quarter's Rock

Priority

Medium

Additional Context

Related discovery: M0 (#37125).