Development record

The tree holds four hand-written longest-run counters for backtick or tilde runs: termsafe's private longestBacktickRun (internal/termsafe/prose.go), internal/core/history/reconstruct_render.go, internal/core/capture/promote.go's codeSpan, and the override fence writer in internal/core/rules (landing with the cut-2 installer branch). The one-canonical-primitive principle forbids a third copy; each is correct today, and each is allowlisted in the code-span canonical test rather than routed through one helper.