Reflection follow-up: rewrite missing substrate file LEARNINGS.md

Missing path: ~/agents/will-engineer/memory/LEARNINGS.md Referenced in: LEARNINGS-PROTOCOL.md lines 11 and 35, and CONVENTIONS.md line 95. Presumed contents: Per-agent institutional memory of mistakes, codebase quirks, and process improvements. LEARNINGS-PROTOCOL.md mandates this file exist and be appended after every trigger event (bug fixed, CI failure, PR feedback, codebase quirk discovery). Format: dated entries with Context/What Happened/Root Cause/Learning/Applied sections. LEARNINGS-PROTOCOL.md warns that Lyra will flag agents with empty LEARNINGS.md after 7 days of active work. Action: create the file with a header and at least the key learnings already documented in daily memory entries (the 6/13 SESSION-LEDGER-PROTOCOL.md silent-file-loss discovery, the 6/14 substrate audit findings, pattern on dual substrate failure modes).