Codex gate: the third derived-push site (Anthropic tool_use content-array branch,
ui.js) still read resultsByTid[tid]||'' without the persisted fallback, so
Anthropic-format sessions could still cold-reload with an empty tool body. Add
the persistedSnippetByTid fallback there too; now all derived result-snippet
reads (OpenAI top-level, Anthropic tool_use, partial) chain to the durable
persisted snippet. Added a guard test asserting EVERY derived resultSnippet read
includes the fallback.