docs: add file system paths reference for /mount/ and s3://fused-users/

[amanbagrecha]

Summary

• Adds a new File system paths page under Guide → Exporting Data, documenting every directory under both the mounted disk (/mount/) and the S3 org space (s3://fused-users/<org>/)
• Covers /mount/fused-system/ (logs, cache, tmp), envs/, lancedb/, duckdb/, root-level UDF ZIP files, and user directories
• Covers s3://fused-system/ subpaths: checkpoints/, fused-cache/, history/, integrations/, job-configs/, logs/, uploaded-files/, and org-level logs/, manifests/, batch-*
• Includes tree diagrams, per-directory file schemas, and code examples for browsing and querying logs with glob and DuckDB
• Adds sidebar entry under "Exporting Data" after "Audit Logs"

Test plan

• Page renders correctly at /guide/data-input-outputs/export-api/log-file-paths
• Sidebar entry "File system paths" appears under Exporting Data after Audit Logs
• All internal links resolve (storage, audit-logs, debugging-playbook, file-explorer, canvas-checkpoints)
• Code blocks display with line numbers
• Tree diagrams render in monospace

🤖 Generated with Claude Code

[MaxLenormand]

Add the titles like Job-configs as H3 so they show up in search in the docs when people do Cmd + K