docs: Audit and update upload documentation

Executed content-audit-agent. Audited content/docs/guides/upload-content.md against code. Added technical details about multipart uploads and troubleshooting steps.

Co-authored-by: PR0M3TH3AN <[email protected]>

docs/agents/task-logs/daily/2026-02-14_00-00-00_content-audit-agent_completed.md

@@ -0,0 +1,24 @@
+# Agent Completion Log
+
+- **Agent:** content-audit-agent
+- **Cadence:** daily
+- **Date:** 2026-02-14
+- **Status:** Completed
+- **Branch:** agents/daily/content-audit-agent
+
+## Summary
+Audited `content/docs/guides/upload-content.md` against the codebase. Verified claims regarding file types, size limits, and metadata fields.
+
+Updates made to documentation:
+1.  **Multipart Upload**: Clarified that direct uploads use multipart upload for reliability.
+2.  **Concurrency**: Added a note about the "one upload at a time" constraint.
+3.  **Troubleshooting**: Added "Invalid S3 Settings" error message.
+
+## Artifacts
+- `artifacts/docs-audit/2026-02-14/inventory.md`
+- `artifacts/docs-audit/2026-02-14/verification.md`
+- `artifacts/docs-audit/2026-02-14/validation.md`
+- `context/CONTEXT_2026-02-14.md`
+- `todo/TODO_2026-02-14.md`
+- `decisions/DECISIONS_2026-02-14.md`
+- `test_logs/TEST_LOG_2026-02-14.md`