feat(pi-overflow): 新增统一的新工具结果展示截断扩展

此前截断分散在多层且互相冲突：Pi bash 保留尾部 50KB，RTK 兜底截断又只留
开头 12000 字符（砍掉报错与完整输出路径），pi-chrome 截开头 30K，web_fetch
各 provider 不一致。新扩展统一负责"新结果给模型看多少"：
- capture.ts 最先加载暂存原文，index.ts 最后加载（system-prompt 之前）
- 超过 24K 字符时原文落盘 <agentDir>/my-pi/pi-overflow/（700/600、原子写），
  优先取 bash fullOutputPath 完整文件；模型看到 头 + 中段信号行 + 尾 的有界
  视图，行号基于落盘原文、结尾永远可见
- overflow_query：按 id 正则搜索、行区间、jsonPath 只读查询，id 校验防穿越
- 收编：RTK truncate 默认关闭、删除 pi-chrome truncateText、web_fetch 默认
  每页 20000（上限 100000）、web_search max_results 限定 1–20
- pi-compaction 遮蔽带 details.overflow.id 的结果时在占位符提示 overflow_query
- 登记 tools.jsonc / routing / 权限 allow / tool-search 常驻与分组

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

pi-overflow/settings.ts

@@ -0,0 +1,100 @@
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+
+export interface OverflowSettings {
+	enabled: boolean;
+	thresholdChars: number;
+	headLines: number;
+	tailLines: number;
+	maxSignalLines: number;
+	signalPattern: string;
+	signalRegex: RegExp;
+	maxLineChars: number;
+	exemptTools: string[];
+	retentionDays: number;
+	maxStoreBytes: number;
+	maxEntryBytes: number;
+}
+
+export const DEFAULT_SIGNAL_PATTERN =
+	"\\b(error|errors|fail|failed|failure|warn|warning|exception|traceback|panic|fatal)\\b";
+
+export const OVERFLOW_DEFAULTS = {
+	enabled: true,
+	thresholdChars: 24_000,
+	headLines: 40,
+	tailLines: 120,
+	maxSignalLines: 40,
+	signalPattern: DEFAULT_SIGNAL_PATTERN,
+	maxLineChars: 500,
+	exemptTools: ["read", "edit", "write", "overflow_query", "ask_user_question"],
+	retentionDays: 7,
+	maxStoreBytes: 1_073_741_824,
+	maxEntryBytes: 67_108_864,
+} as const;
+
+// Bundle-level `config/` is the single source of truth: the extension reads
+// `config/pi-overflow.json` from inside the installed bundle (resolved
+// relative to this package-root source file), never `settings.json`.
+export const OVERFLOW_CONFIG_PATH = fileURLToPath(
+	new URL("../config/pi-overflow.json", import.meta.url),
+);
+
+function isObject(value: unknown): value is Record<string, unknown> {
+	return value !== null && typeof value === "object" && !Array.isArray(value);
+}
+
+function bool(value: unknown, fallback: boolean): boolean {
+	return typeof value === "boolean" ? value : fallback;
+}
+
+function intInRange(value: unknown, fallback: number, min: number, max: number): number {
+	return typeof value === "number" && Number.isInteger(value) && value >= min && value <= max
+		? value
+		: fallback;
+}
+
+function compileSignalPattern(value: unknown): { pattern: string; regex: RegExp } {
+	const pattern = typeof value === "string" && value.length > 0 ? value : DEFAULT_SIGNAL_PATTERN;
+	try {
+		return { pattern, regex: new RegExp(pattern, "i") };
+	} catch {
+		return { pattern: DEFAULT_SIGNAL_PATTERN, regex: new RegExp(DEFAULT_SIGNAL_PATTERN, "i") };
+	}
+}
+
+function stringList(value: unknown, fallback: readonly string[]): string[] {
+	if (!Array.isArray(value)) return [...fallback];
+	const list = value.filter((item): item is string => typeof item === "string" && item.length > 0);
+	return [...new Set(list)];
+}
+
+/**
+ * Read `config/pi-overflow.json`. Every field is validated independently and
+ * falls back to its bundle default when missing or invalid; an unreadable or
+ * non-object file yields all defaults. Tests inject an explicit path.
+ */
+export function readOverflowSettings(configPath: string = OVERFLOW_CONFIG_PATH): OverflowSettings {
+	let parsed: unknown = {};
+	try {
+		parsed = JSON.parse(readFileSync(configPath, "utf8"));
+	} catch {
+		parsed = {};
+	}
+	const config = isObject(parsed) ? parsed : {};
+	const signal = compileSignalPattern(config.signalPattern);
+	return {
+		enabled: bool(config.enabled, OVERFLOW_DEFAULTS.enabled),
+		thresholdChars: intInRange(config.thresholdChars, OVERFLOW_DEFAULTS.thresholdChars, 1, 10_000_000),
+		headLines: intInRange(config.headLines, OVERFLOW_DEFAULTS.headLines, 0, 10_000),
+		tailLines: intInRange(config.tailLines, OVERFLOW_DEFAULTS.tailLines, 0, 10_000),
+		maxSignalLines: intInRange(config.maxSignalLines, OVERFLOW_DEFAULTS.maxSignalLines, 0, 1_000),
+		signalPattern: signal.pattern,
+		signalRegex: signal.regex,
+		maxLineChars: intInRange(config.maxLineChars, OVERFLOW_DEFAULTS.maxLineChars, 10, 100_000),
+		exemptTools: stringList(config.exemptTools, OVERFLOW_DEFAULTS.exemptTools),
+		retentionDays: intInRange(config.retentionDays, OVERFLOW_DEFAULTS.retentionDays, 0, 3_650),
+		maxStoreBytes: intInRange(config.maxStoreBytes, OVERFLOW_DEFAULTS.maxStoreBytes, 1_024, 1_099_511_627_776),
+		maxEntryBytes: intInRange(config.maxEntryBytes, OVERFLOW_DEFAULTS.maxEntryBytes, 1_024, 1_099_511_627_776),
+	};
+}