Runtime system-reminder claims to supersede CLAUDE.md project instructions

A system-reminder is injected mid-session (twice appended to tool results, once with no tool call) instructing Co-Authored-By and 'Generated with Claude Code' trailers, prefixed 'this replaces any earlier attribution guidance'. The project CLAUDE.md explicitly forbids attribution trailers and states it overrides harness defaults. Verified locally: no hooks, no MCP servers, no plugins enabled, and the string exists nowhere on disk. The text is model-keyed (Opus 5 in one session, Sonnet 5 in another), so it is generated by the harness. Request: project-level instructions should take precedence over default attribution guidance, and defaults should not assert that they replace them.