Merge branch 'claude/web-llm-pi-ai-config-385e24' into claude/pi-ai-model-discovery

# Conflicts:
#	docs/core-data-structures/core.i18n.yaml
#	docs/event-producer-consumer.md

docs/core-data-structures/core.md

@@ -160,12 +160,84 @@ Where a message came from is itself a merge-extensible sum type:
  */
 interface MessageSourceMap {
   user: { kind: 'user' }
-  plugin: { kind: 'plugin'; plugin: string }
+  plugin: { kind: 'plugin'; plugin: string } & ContextFormed
   model: ModelMessageSource
   tool: ToolMessageSource
 }
 ```
 
+Provenance and shape are two independent axes. `kind` answers *who produced this*; the optional `form` a producer mixes in answers *what shape of information it is*, so several producers may share one presentation and one producer may emit more than one shape over a session. The vocabulary is semantic and grows one value at a time; an absent or unrecognized value is the documented default, presented as opaque content:
+
+```ts type-equiv
+/**
+ * What SHAPE of information a producer-supplied context carries, declared by
+ * the producer beside its provenance.
+ *
+ * `MessageSource.kind` answers *who produced this*; `form` answers *what kind
+ * of thing it is*, and the two axes are deliberately independent — several
+ * producers share one form (three snapshot producers today), and one producer
+ * may emit more than one form over a session.
+ *
+ * The vocabulary is SEMANTIC, never visual: a value states that the content is
+ * a file's instructions or a catalog of available items, and a consumer decides
+ * what that looks like. Colors, icons, ordering, and collapse defaults are the
+ * consumer's business and must not enter this union. It grows one value at a
+ * time as producers gain the structured fields their form needs; an absent or
+ * unknown value is the documented default, presented as opaque content.
+ */
+type ContextForm =
+  /** Instructions read out of workspace files the model is expected to follow. */
+  | 'instructions'
+  /** A catalog of items available in this session, republished as it changes. */
+  | 'catalog'
+  /** Current state, where a later snapshot from the same producer supersedes an earlier one. */
+  | 'snapshot'
+  /** A one-off account of something that just happened; it supersedes nothing. */
+  | 'notice'
+  /** A message another agent addressed to this one. */
+  | 'relay'
+  /** Material lifted out of another session's log, possibly reduced on the way in. */
+  | 'recall'
+```
+
+```ts type-equiv
+/** One named contribution to a `snapshot`-form context, in assembly order. */
+interface ContextSnapshotSection {
+  /** The contributing subsystem's name. */
+  readonly name: string
+  /** That contribution's model-facing text, exactly as assembled. */
+  readonly text: string
+}
+```
+
+```ts type-equiv
+/**
+ * Producer-declared {@link ContextForm} and the fields that form requires,
+ * mixed into the source shapes that carry one.
+ *
+ * Discriminated by `form` so a producer cannot declare a shape without the
+ * facts that shape is presented from: a `notice` must record its one-line
+ * account, a `snapshot` its sections. Omitting `form` stays valid — an
+ * undeclared context is the documented default.
+ */
+type ContextFormed =
+  | { readonly form?: never }
+  | { readonly form: 'instructions' }
+  | { readonly form: 'catalog' }
+  | {
+    readonly form: 'snapshot'
+    /** The named contributions this snapshot assembled, in order. */
+    readonly sections: readonly ContextSnapshotSection[]
+  }
+  | {
+    readonly form: 'notice'
+    /** One-line account of what happened, shown without expanding the row. */
+    readonly summary: string
+  }
+  | { readonly form: 'relay' }
+  | { readonly form: 'recall' }
+```
+
 ## Streaming
 
 Adapters emit a raw **chunk** protocol; the loop logs the chunks (replay fidelity) while feeding the same chunks through a `BlockAssembler` to rebuild blocks and messages. `StreamChunk` is a closed discriminated union over `type` — `block-start`, `text-delta`, `reasoning-delta`, `tool-call-delta`, `block-end`, `usage`, `finish`.