Indexer allocation safety guard

• Status: Accepted
• Date: 2026-02-01
• Context:
  • Motivation: Prevent unbounded allocations in indexer handlers and satisfy security review feedback.
  • Constraints: No new dependencies; errors must use constant messages with structured context.
• Decision:
  • Add a shared allocation helper that reads MemAvailable from /proc/meminfo and limits requested allocations to 80% of available memory.
  • Apply the helper to dynamic list normalization in search profiles, policy rules, and media domain allowlists, while raising per-list caps to avoid overly constraining users.
  • Dependency rationale: none (std-only implementation).
• Consequences:
  • Positive outcomes: safer allocations, explicit error reporting with context, consistent limits.
  • Risks or trade-offs: allocation checks fail closed if MemAvailable cannot be read; rollback by relaxing the guard to a fixed ceiling if needed.
• Follow-up:
  • Implementation tasks: add helper module, update normalization paths, add unit tests.
  • Test coverage summary: unit tests for allocation guard and meminfo parsing.
  • Observability updates: none required; errors carry context fields for diagnostics.