fix(feedback): address backend review gaps

docs/subsystems/feedback.md

@@ -6,6 +6,183 @@ English | [中文](feedback.zh.md)
 
 Source: [`packages/feedback/message-feedback/src/types.ts`](../../packages/feedback/message-feedback/src/types.ts)
 
+## Public types
+
+```ts type-equiv
+/** Opaque compare-and-set token for one exact feedback item revision. */
+type MessageFeedbackVersion = Branded<'MessageFeedbackVersion'>
+```
+
+```ts type-equiv
+/** The human's overall judgment of one assistant message. */
+type MessageFeedbackRating = 'positive' | 'negative'
+```
+
+```ts type-equiv
+/** One current feedback value and its opaque mutation token. */
+interface MessageFeedbackItem {
+  /** Stable identity of the assistant message inside the owning Session. */
+  readonly messageId: MessageId
+  /** Overall positive or negative judgment. */
+  readonly rating: MessageFeedbackRating
+  /** Optional explanation, preserved verbatim after validation. */
+  readonly note?: string
+  /** Equality-only token replaced by every material create or update. */
+  readonly version: MessageFeedbackVersion
+  /** Host-assigned creation time in Unix epoch milliseconds. */
+  readonly createdAt: number
+  /** Host-assigned time of the most recent material update. */
+  readonly updatedAt: number
+}
+```
+
+```ts type-equiv
+/** Read all message feedback belonging to one persisted Session lifecycle. */
+interface MessageFeedbackListRequest {
+  /** Persisted Session whose sidecar should be read. */
+  readonly sessionId: SessionId
+}
+```
+
+```ts type-equiv
+/** Current feedback values for one Session, in first-creation order. */
+interface MessageFeedbackListValue {
+  /** Fresh immutable item snapshots. */
+  readonly items: readonly MessageFeedbackItem[]
+}
+```
+
+```ts type-equiv
+/** Create or replace feedback for one assistant message. */
+interface MessageFeedbackPutRequest {
+  /** Persisted Session that owns the target message. */
+  readonly sessionId: SessionId
+  /** Target assistant-message identity. */
+  readonly messageId: MessageId
+  /** Desired overall judgment. */
+  readonly rating: MessageFeedbackRating
+  /** Optional non-blank explanation. */
+  readonly note?: string
+  /** Observed item version, or `null` to require that no item exists. */
+  readonly ifVersion: MessageFeedbackVersion | null
+}
+```
+
+```ts type-equiv
+/** Delete feedback for one message after observing its current version. */
+interface MessageFeedbackDeleteRequest {
+  /** Persisted Session that owns the sidecar. */
+  readonly sessionId: SessionId
+  /** Message whose feedback should be absent after this operation. */
+  readonly messageId: MessageId
+  /** Observed item version; ignored when the item is already absent. */
+  readonly ifVersion: MessageFeedbackVersion
+}
+```
+
+```ts type-equiv
+/** Idempotent deletion acknowledgement. */
+interface MessageFeedbackDeleteValue {
+  /** Stable postcondition shared by the first deletion and every retry. */
+  readonly absent: true
+}
+```
+
+```ts type-equiv
+/** No persisted Session header exists for the requested id. */
+interface MessageFeedbackSessionNotFound {
+  readonly code: 'session-not-found'
+  readonly sessionId: SessionId
+}
+```
+
+```ts type-equiv
+/** The id does not name a derived, append-origin assistant message. */
+interface MessageFeedbackTargetNotFound {
+  readonly code: 'target-not-found'
+  readonly sessionId: SessionId
+  readonly messageId: MessageId
+}
+```
+
+```ts type-equiv
+/** A material mutation did not match the addressed item's current version. */
+interface MessageFeedbackVersionConflict {
+  readonly code: 'version-conflict'
+  /** Authoritative current item, or `null` when it does not exist. */
+  readonly current: MessageFeedbackItem | null
+}
+```
+
+```ts type-equiv
+/** A supplied note contains no non-whitespace character. */
+interface MessageFeedbackNoteBlank {
+  readonly code: 'note-blank'
+}
+```
+
+```ts type-equiv
+/** A supplied note exceeds the configured UTF-8 byte limit. */
+interface MessageFeedbackNoteTooLarge {
+  readonly code: 'note-too-large'
+  readonly maxBytes: number
+  readonly actualBytes: number
+}
+```
+
+```ts type-equiv
+/** Failures shared by the public message-feedback operations. */
+type MessageFeedbackFailure =
+  | MessageFeedbackSessionNotFound
+  | MessageFeedbackTargetNotFound
+  | MessageFeedbackVersionConflict
+  | MessageFeedbackNoteBlank
+  | MessageFeedbackNoteTooLarge
+```
+
+```ts type-equiv
+/** Successful public operation result. */
+interface MessageFeedbackSuccess<T> {
+  readonly ok: true
+  readonly value: T
+}
+```
+
+```ts type-equiv
+/** Rejected public operation result with a stable business failure. */
+interface MessageFeedbackRejected<E extends MessageFeedbackFailure> {
+  readonly ok: false
+  readonly error: E
+}
+```
+
+```ts type-equiv
+/** Result returned by the message-feedback `list` operation. */
+type MessageFeedbackListResult =
+  | MessageFeedbackSuccess<MessageFeedbackListValue>
+  | MessageFeedbackRejected<MessageFeedbackSessionNotFound>
+```
+
+```ts type-equiv
+/** Result returned by the message-feedback `put` operation. */
+type MessageFeedbackPutResult =
+  | MessageFeedbackSuccess<MessageFeedbackItem>
+  | MessageFeedbackRejected<
+    | MessageFeedbackSessionNotFound
+    | MessageFeedbackTargetNotFound
+    | MessageFeedbackVersionConflict
+    | MessageFeedbackNoteBlank
+    | MessageFeedbackNoteTooLarge
+  >
+```
+
+```ts type-equiv
+/** Result returned by the message-feedback `delete` operation. */
+type MessageFeedbackDeleteResult =
+  | MessageFeedbackSuccess<MessageFeedbackDeleteValue>
+  | MessageFeedbackRejected<MessageFeedbackSessionNotFound | MessageFeedbackVersionConflict>
+```
+
 ## Data and concurrency
 
 One Session sidecar row contains its header identity `{createdAt, cwd}` and feedback items keyed by `MessageId`. Each item carries a positive or negative rating, an optional note, Host-assigned `createdAt`/`updatedAt` timestamps, and its own opaque version. Versions are compared only for equality and only against the addressed message; callers do not order or synthesize them.
@@ -22,12 +199,15 @@ The stored `{createdAt, cwd}` identity must match the inspected header. A mismat
 
 The service stores whole Session rows in the `message_feedback` storage domain through `ctx.storageDomain`. Before `put` commits a row that references a target message, a matching live target passes through the canonical `ctx.sessions.flush` checkpoint; both live and cold paths are then physically read from sequence zero through `SessionPersistence.readFrom`. The resulting observation is revalidated before the sidecar write, so the durable target log always precedes its sidecar commit. `maxNoteBytes` is required and bounds note text by UTF-8 bytes; the Web Host composition sets `8192`. The package publishes the Host `messageFeedback.list`, `messageFeedback.put`, and `messageFeedback.delete` unary Remote contract through `GatewayService` and `@Remote`; the generated Cordis surface below is the method-level authority.
 
+Plugin disposal closes mutation admission, drains accepted per-Session queue work, and then closes the storage domain.
+
 ## Boundaries and limitations
 
 - The client Remote aggregate mount and UI consumer are separately owned and deferred.
 - The mutation queue is process-local. Storage-domain has no cross-process conditional write, so multiple Host writers to one storage root have no compare-and-swap or lost-update guarantee.
 - Session persistence has no durable deletion surface. The service does not treat `session/disposed` or `host/session-removed` as deletion and therefore performs no fake cascade; orphan sidecar rows may remain after out-of-band log removal.
 - A request in the narrow interval after live detach but before the persistence catalog materializes the header can receive `session-not-found`; callers retry after retirement materialization.
+- Cold requests scan the complete Session snapshot catalog because persistence has no lookup-by-id metadata operation. One Session row also has no item-count or aggregate-byte cap; `maxNoteBytes` bounds only each note until a concrete consumer owns a row policy.
 - Header identity detects a reused id only when `{createdAt, cwd}` differs; a cloned log retaining the same header identity is indistinguishable by this contract.
 - The Host contract records no authenticated actor or audit identity and therefore assumes a trusted caller boundary.