feat(insert_assets): 资产可标记是否与当前任务相关(related)

insert_assets 每条资产新增 related 入参(默认 true)：仅在任务开启资产
覆盖度功能时生效——true 才自动纳入覆盖度(测试范围分母)，false 则只入
共享资产库、不计入本任务覆盖度(如顺带发现的旁站/无关资产)。

- Call 内部按 related + coverageDisabled 双重 gate 决定是否 AddAutoScope
- 覆盖度关闭时 related 无意义，经 StripCoverageParams 从最终工具 schema
  剔除(必须在 ToolResolve 的 DB schema 覆盖之后做，故在装配链末端处理)
- 旧库经 refreshBuiltinToolSchemas(flag v6) 刷新 insert_assets schema，
  否则首插入only 的 seed 收不到新参数
- 补 StripCoverageParams 回归测试(开启保留/关闭隐藏/不改原始 schema)

Claude-Session: https://claude.ai/code/session_01Jm87Gr5fq5aso6SfLyguhx

agent/tools.go

@@ -186,6 +186,60 @@ func (t *ToolSet) DropCoverageTools(tools []actool.CoreTool) []actool.CoreTool {
 	return out
 }
 
+// StripCoverageParams hides coverage-only parameters (currently insert_assets'
+// per-item `related`, which only decides whether an asset enters the coverage
+// denominator) from the model-facing schema when coverage is disabled — the param
+// has no effect then, so showing it just pollutes the prompt. MUST run on the FINAL
+// tool list (after AugmentTools/ToolResolve): the DB tools table is authoritative on
+// schema, so stripping the code schema earlier would be overwritten. No-op when
+// enabled or when the list has no insert_assets. The schema is deep-copied before
+// editing so the shared/DB schema map is never mutated.
+func (t *ToolSet) StripCoverageParams(tools []actool.CoreTool) []actool.CoreTool {
+	if !t.coverageDisabled {
+		return tools
+	}
+	for i, tool := range tools {
+		if tool.Name() != "insert_assets" {
+			continue
+		}
+		schema := deepCopyJSONMap(tool.InputSchema())
+		if props, ok := nestedMap(schema, "properties", "assets", "items", "properties"); ok {
+			delete(props, "related")
+		}
+		tools[i] = DecorateTool(tool, tool.Description(), schema)
+	}
+	return tools
+}
+
+// deepCopyJSONMap returns a JSON round-trip deep copy of a schema map so callers can
+// edit it without touching the original (which may be shared/cached). Falls back to
+// the input on any marshal error (edits then become best-effort no-ops upstream).
+func deepCopyJSONMap(m map[string]any) map[string]any {
+	b, err := json.Marshal(m)
+	if err != nil {
+		return m
+	}
+	var out map[string]any
+	if json.Unmarshal(b, &out) != nil {
+		return m
+	}
+	return out
+}
+
+// nestedMap walks a chain of string keys through nested map[string]any values,
+// returning the final map and whether the whole path resolved to one.
+func nestedMap(m map[string]any, keys ...string) (map[string]any, bool) {
+	cur := m
+	for _, k := range keys {
+		next, ok := cur[k].(map[string]any)
+		if !ok {
+			return nil, false
+		}
+		cur = next
+	}
+	return cur, true
+}
+
 // Cross-task reuse: exported accessors returning the per-task tool logic bound to
 // THIS ToolSet's store. Host-side orchestration tools build a ToolSet for an
 // arbitrary task, then Call these — so cross-task reads/hint reuse the exact