feat(history): 消息搜索/编辑/删除 + 会话置顶(D2/D3/D5)

- history/message_ops.go(新): Search(会话内, q/after互斥, LIKE参数化+%/_转义+大小写不敏感, 严格限定会话doc) / UpdateMessage(返回更新后Message) / DeleteMessage / messageByID / escapeLike
- history/session_pin.go(新): SetPinned; 迁移0009 chat_sessions加pinned INTEGER DEFAULT 0; store.go SessionMeta.Pinned + createSessionsTable加列
- session_preview.go: 查询加s.pinned + ORDER BY pinned DESC,(type=main) DESC,created_at ASC
- gateway history_write.go(新,保持history.go≤500): handlePatchSession(pinned+title) / handlePatchMessage / handleDeleteMessage; server.go加PATCH/DELETE /api/v1/messages/{id} + /sessions/{id}置顶
- history.go: handleListMessages读q分流Search; 契约PATCH title/置顶
- D2会话内搜索(不做跨会话,隔离会话不外泄红线); D3不做重发端点(客户端编辑后再发); D5用pinned bool
- 测试(message_ops/history_messages/migrate_pinned), build/vet/test绿+3平台交叉编译; Docs/api-client v0.30
- 未做: 编辑/删除WS实时广播(message_edited/deleted), 下批

internal/services/gateway/history.go

@@ -1,12 +1,10 @@
 package gateway
 
 import (
-	"encoding/json"
 	"errors"
 	"net/http"
 	"strconv"
 	"strings"
-	"unicode/utf8"
 
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/auth"
 	apperr "git.yeij.top/AskaEth/Cyrene_v2/internal/errors"
@@ -20,6 +18,9 @@ type historySessionSummary struct {
 	Type      string `json:"type"` // "main" | "sub"
 	Title     string `json:"title,omitempty"`
 	CreatedAt int64  `json:"createdAt"`
+	// Pinned floats the session to the top of the list (D5). It is order metadata
+	// only and is always present so a client can render/sort without a second call.
+	Pinned bool `json:"pinned"`
 	// LastMessage is a display-only preview of the session's newest message, so the
 	// client can render a conversation row (e.g. the Android session list) without a
 	// per-session request. It is omitted for a session with no messages. Content is
@@ -76,6 +77,7 @@ func (s *Server) handleHistorySessions(w http.ResponseWriter, r *http.Request) {
 			Type:        m.Type,
 			Title:       m.Title,
 			CreatedAt:   m.CreatedAt,
+			Pinned:      m.Pinned,
 			LastMessage: toHistoryLastMessage(m.LastMessage),
 		})
 	}
@@ -122,8 +124,11 @@ func (s *Server) handleCreateSubSession(w http.ResponseWriter, r *http.Request)
 //     one-page limit of a backward walk.
 //
 // limit defaults to 50 (clamped to 200) for both directions. platform filters the page
-// by source platform in either direction. Supplying both before and after (both > 0)
-// answers 400, as does a non-numeric/negative after or an invalid limit/before.
+// by source platform in either direction. An optional q switches the page to a
+// session-scoped content search (newest first, still honoring before/limit); q is
+// mutually exclusive with after, and an empty q is ignored so plain paging is
+// unchanged. Supplying both before and after (both > 0) answers 400, as does a
+// non-numeric/negative after or an invalid limit/before.
 func (s *Server) handleListMessages(w http.ResponseWriter, r *http.Request) {
 	if s.history == nil {
 		writeError(w, &apperr.AppError{Code: "not_implemented", Message: "会话历史服务未配置（未注入 HistoryStore）", HTTPCode: http.StatusNotImplemented})
@@ -163,12 +168,20 @@ func (s *Server) handleListMessages(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	platform := r.URL.Query().Get("platform")
+	query := strings.TrimSpace(r.URL.Query().Get("q"))
+	if query != "" && after > 0 {
+		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "q and after are mutually exclusive"))
+		return
+	}
 
 	var msgs []history.Message
 	var err error
-	if after > 0 {
+	switch {
+	case query != "":
+		msgs, err = s.history.Search(r.Context(), id, query, before, limit)
+	case after > 0:
 		msgs, err = s.history.ListAfter(r.Context(), id, after, limit, platform)
-	} else {
+	default:
 		msgs, err = s.history.List(r.Context(), id, before, limit, platform)
 	}
 	if err != nil {
@@ -322,57 +335,6 @@ func (s *Server) handleDeleteSession(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"deleted": id})
 }
 
-// renameSessionRequest is the PATCH /api/v1/sessions/{id} body.
-type renameSessionRequest struct {
-	Title string `json:"title"`
-}
-
-// maxSessionTitleRunes bounds a client-supplied session title so a display row never
-// overflows. It is a display-only bound: identity and permissions never derive from
-// the title (project red line).
-const maxSessionTitleRunes = 80
-
-// handleRenameSession renames a persistent session (main or sub). The title is
-// display-only metadata, so unlike DELETE it is allowed on the fixed main session. An
-// empty/whitespace title or one longer than maxSessionTitleRunes answers 400; an
-// unknown session id answers 404. It is owner/admin-gated like the other history
-// writes.
-func (s *Server) handleRenameSession(w http.ResponseWriter, r *http.Request) {
-	if s.history == nil {
-		writeError(w, &apperr.AppError{Code: "not_implemented", Message: "会话历史服务未配置（未注入 HistoryStore）", HTTPCode: http.StatusNotImplemented})
-		return
-	}
-	id := r.PathValue("id")
-	if id == "" {
-		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "session id is required"))
-		return
-	}
-	var req renameSessionRequest
-	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
-		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "invalid request body"))
-		return
-	}
-	title := strings.TrimSpace(req.Title)
-	if title == "" {
-		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "title is required"))
-		return
-	}
-	if utf8.RuneCountInString(title) > maxSessionTitleRunes {
-		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "title is too long (max 80 characters)"))
-		return
-	}
-	if err := s.history.RenameSession(r.Context(), id, title); err != nil {
-		if errors.Is(err, history.ErrSessionNotFound) {
-			writeError(w, apperr.Wrap(apperr.ErrNotFound, "not_found", "session %q not found", id))
-			return
-		}
-		s.log.Error("history rename session", "err", err, "session", id)
-		writeError(w, apperr.Wrap(apperr.ErrInternal, "session_failed", "failed to rename session"))
-		return
-	}
-	writeJSON(w, http.StatusOK, map[string]any{"id": id, "title": title})
-}
-
 // toHistoryMessage maps a stored history.Message to its wire shape.
 func toHistoryMessage(m history.Message) historyMessage {
 	return historyMessage{