// Package sessionread implements the design/22 §8-3「主动读取其他会话上下文」tool: the
// running role may pull another session's recent messages as *external, read-only
// material*, rendered with a fixed attribution header so she can never mistake
// someone else's words for her own memory or her own voice (design/22 §8.1).
//
// Read-only by construction, not by discipline: the package depends on narrow
// interfaces that declare read calls only (HistoryReader, PersonaNamer) and never
// touches internal/persona/registry directly, so no write — memory write, message
// append, read-cursor advance, broadcast — is reachable from inside. It also never
// logs message bodies; only attribution metadata (design/22 §8.1 约束 4).
//
// Access is fail-closed (design/22 §8.1 约束 3): the calling conversation must be
// the owner's, and only the Web main session ("web") and Web sub sessions
// ("web:<uuid>") may be read. Every other session id — the IM group and stranger
// sessions in particular — is rejected, and an absent session is a hard error
// rather than empty material, so "read nothing" can never pass for "they said
// nothing".
//
// The tool is registered by cmd/cyrene (wireSessionReadTool) and reaches the model
// through the internal/runtime/tool dispatcher like any other tool.
package sessionread