docs: cross-reference the boundary-failure record family

[chaksaray]

Closes #232. Adds a cross-reference sentence to each of the 8 records PR #224 identified as the same missing content-versus-instruction boundary at different entry points: AVE-2026-00002, 00016, 00020, 00028, 00041, 00043, 00044, 00065.

Text-only, no schema change, per Finding 3's conclusion that this corpus's real gaps are prose, not structure.

Each of the 8 gets its own specific entry-point phrasing rather than identical pasted text:

• 00002: tool-description field, read at discovery, before any tool call
• 00016: retrieved document content, injected at RAG query time
• 00020: sub-agent input, in an A2A delegation chain
• 00028: uploaded document content, directed to be treated as instructions
• 00041: MCP server-card, fetched at connection time, outside runtime monitoring
• 00043: gap between the rendered UI surface and the metadata the model reads
• 00044: async task result payload, read across a temporal gap
• 00065: A2A agent-card self-declared metadata

00065 already carried a differentiation sentence contrasting itself with 00041; the new family cross-reference is appended after it rather than replacing it.

Validated:

• python scripts/validate_records.py: 80/80 valid (only pre-existing, unrelated researcher-attribution warnings)
• python scripts/check_fixtures.py: all pass
• python -m pytest tests/ -x -q: 427 passed

Real, current description text pulled fresh from dist/ave-records-latest.json before editing, confirmed unchanged since the audit ran.