perf(session-controller): exclude the shared image limits from session summaries

`imageLimits` is a boot constant every Session shares: the unit stores no
per-Session state (`stateSchema: z.null()`, `apply: state => state`) and its
view returns `ctx.attachments.imageLimits`. A list row therefore repeated one
host-wide capability fact on every row. It now carries the summary mark like
the three log-derived units, so a summary read skips it while an opened Session
still receives it through `session/follow`, the control baseline, and
`session.projections`.

No other logic changes: the registration, its schema, its constant view, and
the host-side prompt validation keep reading `ctx.attachments` directly.

packages/api/session-controller/src/list.ts

@@ -98,6 +98,7 @@ export class ApiSessionList {
         wire: {
           viewSchema: imageLimitsSchema,
           view: () => attachmentCtx.attachments.imageLimits,
+          summary: false,
         },
         stateVersion: 1,
       })

packages/api/session-controller/src/types.ts

@@ -8,7 +8,7 @@ import type { Branded } from '@deepseek-ai/dsh-brand'
 import type { LlmAttemptId, MessageId } from '@deepseek-ai/dsh-llm/brand'
 import type { TextBlock } from '@deepseek-ai/dsh-llm'
 import type { SessionId, SessionSeqCursor } from '@deepseek-ai/dsh-session/types'
-import type { SessionProjectionMap } from '@deepseek-ai/dsh-session-projection/types'
+import type { SessionProjectionMap, SessionProjectionSummaryExcluded } from '@deepseek-ai/dsh-session-projection/types'
 import type { Principal } from '@deepseek-ai/dsh-typert-protocol'
 import type { JsonValue } from '@deepseek-ai/dsh-util-values'
 import type { WorkspaceId } from '@deepseek-ai/dsh-workspace/types'
@@ -25,8 +25,12 @@ declare module '@deepseek-ai/dsh-session-projection/types' {
   interface SessionProjectionMap {
     /** Persisted facts used to summarize a Session without activating it. */
     sessionListMetadata: SessionListMetadata
-    /** Image-intake limits enforced by the Session prompt endpoint. */
-    imageLimits: ImageAttachmentLimits
+    /**
+     * Image-intake limits enforced by the Session prompt endpoint. Boot
+     * constant, excluded from Session summary payloads: every Session shares
+     * it, so a list row would repeat one host-wide fact.
+     */
+    imageLimits: SessionProjectionSummaryExcluded<ImageAttachmentLimits>
     /** Durable model selection already used and selected for the next request. */
     modelSelection: ModelSelectionProjection
   }