cleanup(web): drop the unimplemented user-message edit control

The user bubble's IconActions row carried an edit button with no click
handler, no client mutation, and no host operation behind it, advertising
an affordance the product cannot honor. The row now renders clock / copy /
branch only for both user and assistant chrome, and MessageIconActions
loses the `edit` prop with the button.

The package README records the missing capability under Known Limitations,
the web aria goldens pin the row without the control, and the Agent Note
states what must exist before it comes back.

.agents/notes/implemented/simplification/2026-07-31-drop-user-message-edit-stub.i18n.yaml

@@ -0,0 +1,6 @@
+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# side as of the last confirmed-consistent state. Both languages carry equal authority;
+# after editing either side, bring the other along and re-record with:
+#   pnpm run verify-translation-pairing --write .agents/notes/implemented/simplification/2026-07-31-drop-user-message-edit-stub.md
+2026-07-31-drop-user-message-edit-stub.md: 5a34be1dd285f4aced9e6cfb2e324b20ec734bed
+2026-07-31-drop-user-message-edit-stub.zh.md: 768cb4618b4a85f61e6348f8c6fb6a93d686e7d3

.agents/notes/implemented/simplification/2026-07-31-drop-user-message-edit-stub.md

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+# Agent Note: Drop the user-message edit stub
+
+Status: implemented
+
+English | [中文](2026-07-31-drop-user-message-edit-stub.zh.md)
+
+## Problem
+
+The user bubble's IconActions row carried an edit button beside copy and branch. Nothing backed it: the control had no click handler, no client mutation, and no host operation for resending an edited message. A user who found it saw an affordance the product cannot honor.
+
+## Decision
+
+`MessageIconActions` renders clock / copy / branch only, and its `edit` prop is gone with the button; `MessageItem` no longer passes it. The user bubble and the assistant chrome now differ only by clock side. The package README records the missing capability under Known Limitations, and the web message-actions golden pins the row without the control.
+
+The common locale keeps its generic `edit` term, which is shared vocabulary rather than this component's copy.
+
+Reintroduce the control together with the capability: a client mutation that edits a settled user message and the host behavior that decides what the edited message does to the turn that already consumed it.
+
+## Alternatives considered
+
+**Disable the button with a tooltip.** A visible-but-dead control still advertises editing and costs the same explaining; removal is the honest state.
+
+**Wire it to the queue editor.** The queue edits a message that has not been sent. A settled user message is already in the transcript and in the model's context, so reusing that editor would silently mean something else.
+
+## Consequences
+
+Web offers no way to correct a sent message; branching from the message is the nearest available gesture. Reintroduction is a UI-only change once the mutation exists, since the row composes its actions from props.

.agents/notes/implemented/simplification/2026-07-31-drop-user-message-edit-stub.zh.md

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+# Agent Note: 移除 user 消息的编辑存根
+
+Status: implemented
+
+[English](2026-07-31-drop-user-message-edit-stub.md) | 中文
+
+## 问题
+
+user 气泡的 IconActions 行在复制和分支旁边还有一个编辑按钮，但其背后什么都没有：该控件没有点击处理、没有 client 侧变更，也没有 host 侧重新发送已编辑消息的操作。用户找到它时，看到的是一个产品无法兑现的可供性。
+
+## 决策
+
+`MessageIconActions` 只渲染时钟／复制／分支，其 `edit` prop 随按钮一并删除；`MessageItem` 不再传入该 prop。现在 user 气泡与 assistant chrome 只在时钟位置上不同。包 README 在 Known Limitations 中记录这项缺失的能力，web 的 message-actions 金样固定了不含该控件的动作行。
+
+公共 locale 保留通用的 `edit` 词条：它是共享词汇，而非本组件的文案。
+
+重新引入该控件时要与能力一起落地：既需要编辑已定稿 user 消息的 client 变更，也需要 host 侧决定这条编辑后的消息对已经消费过它的轮次意味着什么。
+
+## 曾考虑的替代方案
+
+**把按钮置灰并加提示。** 一个可见但无效的控件仍在宣告可以编辑，解释成本相同；直接移除才是诚实的状态。
+
+**接到队列编辑器上。** 队列编辑的是尚未发送的消息。已定稿的 user 消息已经进入转录和模型上下文，复用该编辑器会让同一个动作悄悄变成另一件事。
+
+## 后果
+
+Web 没有任何途径修正已发送的消息；从该消息分支是最接近的现有手势。由于动作行的内容完全由 props 组合而来，能力就绪后重新引入只是一次纯 UI 改动。