fix(web): address the second review round on context provenance

- An empty replacement catalog is a real catalog: `renderCatalogUpdate()`
  publishes zero entries when the last skill disappears, and falling back
  would hide that every earlier name was retired.
- The opaque fallback keeps a `form` declaration this version cannot present.
  It is the one place a newer or foreign log's declared shape would otherwise
  vanish from the UI entirely, since the row marker is also absent there.
- An instruction change with an unrecognized `action` disqualifies the record.
  The action decides the word the row shows, so an unknown one would be
  presented as loaded or updated.
- The catalog list bounds itself and reports the withheld count. Entry count
  is unbounded and the scrollport bounds height, not node count.
- A catalog message keeps content blocks this version does not know, instead
  of dropping model-visible content the extensible union may carry.
- `core.md` defines `ContextFormed`, the interface actually carrying the
  optional field, beside `ContextForm`.
- The superseded-in-part bullet states the affected clauses as one rule rather
  than enumerating them; two rounds of enumeration each missed some, which is
  the shape being fragile rather than the list being wrong.
- The note records the one migration case that does not self-heal: an
  old-format catalog as the only one, with an empty current view, leaves a
  stale catalog nothing replaces.

.agents/notes/implemented/feature/2026-08-05-context-form-vocabulary.i18n.yaml

@@ -2,5 +2,5 @@
 # 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/feature/2026-08-05-context-form-vocabulary.md
-2026-08-05-context-form-vocabulary.md: 20577b0ad0eaa9eb8dc8528cedd18d15439ad299
-2026-08-05-context-form-vocabulary.zh.md: 154e8ae54fc6b27ce782533b4246d48190639128
+2026-08-05-context-form-vocabulary.md: c111acfec4fa85fe9e25adeb615371d65098f20f
+2026-08-05-context-form-vocabulary.zh.md: d4da218c4c6026eb875513c2acbfcd18ced8faa1

.agents/notes/implemented/feature/2026-08-05-context-form-vocabulary.md

@@ -27,7 +27,7 @@ The vocabulary is semantic, never visual. A value states that the content is a f
 
 Entries record the published fact **unescaped**. The pseudo-XML escaping belongs to the `<available_skills>` frame, which exists for the model, so it is applied when rendering that frame and never stored; otherwise a consumer would have to know the frame's encoding to display a description containing `<`, and the same frame knowledge this decision removes would leak back in another shape. `escapeText` is deterministic and injective, so digesting the unescaped entries preserves republish semantics exactly, and the model-facing text stays byte-identical.
 
-That move also relocates catalog **identity**: the republish digest now covers the durable entries rather than the rendered text, so the model-facing framing can no longer decide whether a republish is needed, and the text-slicing that recovered entries from a logged message is gone. A resumed session whose newest catalog predates this change republishes once, which the pre-release stance permits.
+That move also relocates catalog **identity**: the republish digest now covers the durable entries rather than the rendered text, so the model-facing framing can no longer decide whether a republish is needed, and the text-slicing that recovered entries from a logged message is gone. A resumed session whose newest catalog predates this change republishes once, which the pre-release stance permits. One case does not self-heal: if that old-format catalog is the only one and the current view has no skills, the plugin sees no published catalog and emits no tombstone, so the model keeps a stale catalog nothing replaces. The pre-release stance ("backends reject old on-disk formats") permits it; it is recorded here rather than left to the optimistic path.
 
 Both readers are **all-or-nothing**: one unreadable entry disqualifies the record rather than being dropped, because a body that replaces the model-facing text must not present a confident but incomplete account of what the model read. The row's form marker reports what actually rendered, not what was declared.
 

.agents/notes/implemented/feature/2026-08-05-context-form-vocabulary.zh.md

@@ -27,7 +27,7 @@ Status: implemented
 
 条目记录的是**未转义**的发布事实。伪 XML 转义属于 `<available_skills>` 这层为模型而设的框架，因此只在渲染该框架时施加、从不存储；否则消费方要正确展示含 `<` 的描述就得知道框架的编码方式，本决策刚移除的框架知识会换一种形式泄漏回来。`escapeText` 确定且单射，故对未转义条目取 digest 与此前完全等价，重新发布语义不变，面向模型的文本逐字节不变。
 
-这次迁移同时挪动了目录的**身份**：重新发布用的 digest 现在覆盖持久条目而非渲染文本，于是面向模型的包装再也无法左右是否需要重新发布，那段从已记录消息里切出条目的文本切分逻辑也随之删除。若恢复的会话中最新目录早于本次改动，会重新发布一次——发布前阶段的姿态允许这样做。
+这次迁移同时挪动了目录的**身份**：重新发布用的 digest 现在覆盖持久条目而非渲染文本，于是面向模型的包装再也无法左右是否需要重新发布，那段从已记录消息里切出条目的文本切分逻辑也随之删除。若恢复的会话中最新目录早于本次改动，会重新发布一次——发布前阶段的姿态允许这样做。有一种情形不会自愈：当那份旧格式目录是唯一的一份、且当前视图没有任何 skill 时，插件看不到已发布目录，也就不会发出 tombstone，模型手里会留着一份无人替换的过期目录。发布前阶段的姿态（「后端拒绝旧的磁盘格式」）允许这一点；此处如实记录，而不是只写乐观路径。
 
 两个读取器都是**全有或全无**：一条不可读的条目即判定整条记录不可用，而不是把它丢掉——会替换掉面向模型文本的内容区，不得给出自信但残缺的「模型读到了什么」。行上的形态标记报告的是实际渲染出的形态，而非声明的形态。