Feat: Memory health panel — surface memory usage, truncation warnings & overflow risk in Settings

[cqlxyz]

English:

Background — a real incident: MEMORY.md is the agent's memory index, capped at 25 KB (MAX_INDEX_BYTES in aion-memory). When it exceeds the cap it gets truncated — and in #244 the truncation even panicked mid-UTF-8-char, crashing the whole team runtime (409 TEAM_RUNTIME_NOT_READY), leaving every agent unreachable with zero UI feedback. The panic is fixed in #248, but truncation itself remains silent: users still can't see how full their memory is, when it was truncated, or what was lost.

Proposal — Memory health panel in Settings:

Usage bar: current size / 25 KB cap, entry count
Truncation history: last truncation time + reason
Overflow warning: yellow at 80%, red at 95%
"Reveal in folder" button (open the memory directory)
Why it matters: memory is the agent's core asset; today users have zero visibility into it. A silent truncation can quietly drop memory entries, and (pre-#248) could even take down the whole team. This closes the loop on the #244/#248 incident.

Scope (incremental): aion-memory exposes a small memory stats API (size, line count, truncated flag, last truncation time) → AionUi reads it via bridge → new section in Settings (System/About). Pure addition, no behavior change to existing flows. i18n for all locales.

中文：

背景（真实事故）： MEMORY.md 是 agent 的记忆索引，上限 25KB（aion-memory 的 MAX_INDEX_BYTES）。超过上限会被截断——#244 中截断逻辑甚至在 UTF-8 字符中间 panic，导致整个团队运行时崩溃（409 TEAM_RUNTIME_NOT_READY），所有 agent 失联且界面零提示。panic 已在 #248 修复，但"静默截断"问题依然存在：用户看不到记忆用了多少、何时被截断、丢了什么。

提案 —— 设置页新增「记忆健康面板」：

用量条：当前大小 / 25KB 上限、条目数
截断记录：最近截断时间 + 原因
超限预警：80% 黄 / 95% 红
「在文件夹中显示」按钮（打开 memory 目录）
价值： 记忆是 agent 的核心资产，目前用户零感知。静默截断会悄悄丢记忆条目，（修复前）甚至能搞垮整个团队。此提案为 #244/#248 事故画上闭环。

范围（纯增量）： aion-memory 暴露一个小型 memory stats API（大小/条数/截断标志/最近截断时间）→ AionUi 经 bridge 读取 → 设置页新增区块。不改现有流程行为。全语言 i18n。

[github-actions[bot]]

Thanks for posting! @IceyLiu will take a look soon. / 感谢发帖！@IceyLiu 会尽快跟进。