feat(types): brand bash ids + stop brand erosion; extract Branded to dsh-brand

Type-only change (brands are zero-cost casts; no runtime/wire impact). Closes
the two gaps in the "brand ids that cross package boundaries" policy and fixes
the dependency direction so a capability package never pulls in an unrelated one.

- Extract the `Branded<B>` primitive into a new standalone type-only package
  `@deepseek-ai/dsh-brand` (packages/util/brand) with no harness-package deps.
  dsh-llm keeps its owned CallId but imports Branded from dsh-brand; dsh-session,
  dsh-agent, and dsh-bash all import Branded from there. dsh-bash depends on
  dsh-brand ALONE — never on dsh-llm or dsh-session (the architectural fix: a
  generic execution backend must not couple to the LLM or session vocabulary).
- Mint BashTaskId + OwnerToken in dsh-bash and thread them through BashTask.id,
  the get/ownerOf/list/readOutput/kill seam, the bash-local generation site, and
  the dsh-tool-bash validate/access surface. OwnerToken is a DISTINCT brand from
  SessionId so the seam stays decoupled; dsh-tool-bash is the single boundary
  that casts SessionId -> OwnerToken.
- Brand at the SOURCE, not via mid-pipeline casts: agent-loop's Config types
  agents[].id as AgentId and resumeSessionId as SessionId, so the brand enters
  at the config boundary and the inner create()/resume casts disappear (only the
  genuinely-new per-run session-id string is cast).
- Stop brand erosion: propagate CallId/SessionId/AgentId to the registry/store
  Map keys and public params/exports (SessionStore, AgentRegistry + factory
  options, the ACP session-id surface + ToolPresenter CallId map, the
  persistence coordinator, invariants pendingCalls, the pi-ai tool-call maps).
- Docs: document BashTaskId/OwnerToken in bash.md (type-equiv re-pasted), point
  the Branded type-equiv at dsh-brand, fix stale param types in the session/
  agent/bash READMEs, regenerate the cordis catalog + module graph.

Implements docs/rfc/proposed/architecture/2026-06-20-branded-ids.md

packages/core/session/src/index.ts

@@ -220,7 +220,7 @@ export class Session {
  * subscribe to `session/event` and flush on `session/flush` / dispose.
  */
 export class SessionStore extends Service {
-  private store = new Map<string, Session>()
+  private store = new Map<SessionId, Session>()
   private counter = 0
 
   constructor(ctx: Context) {
@@ -244,7 +244,7 @@ export class SessionStore extends Service {
    * @throws if a session with `id` already exists, or if `meta.cwd` is a
    *   non-absolute path (storage backends key directories off it).
    */
-  create(id?: string, options?: CreateSessionOptions): Session {
+  create(id?: SessionId, options?: CreateSessionOptions): Session {
     const session = this.prepare(id, options)
     // Single effect owned by the calling fiber. Yield the detach BEFORE
     // announcing so a throwing `session/created` listener rolls the attach back
@@ -269,7 +269,7 @@ export class SessionStore extends Service {
    * @throws if a session with `id` already exists, or if `meta.cwd` is a
    *   non-absolute path.
    */
-  prepare(id?: string, options?: CreateSessionOptions): Session {
+  prepare(id?: SessionId, options?: CreateSessionOptions): Session {
     const sessionId = SessionId(id ?? `session-${++this.counter}`)
     if (this.store.has(sessionId)) throw new Error(`session "${sessionId}" already exists`)
     const cwd = options?.meta?.cwd
@@ -321,7 +321,7 @@ export class SessionStore extends Service {
     this.ctx.emit('session/created', session)
   }
 
-  get(id: string): Session | undefined {
+  get(id: SessionId): Session | undefined {
     return this.store.get(id)
   }
 

packages/core/session/src/types.ts

@@ -1,4 +1,5 @@
-import type { Branded, CallId, ContentBlock, MessageSource, StreamChunk, TokenUsage } from '@deepseek-ai/dsh-llm'
+import type { Branded } from '@deepseek-ai/dsh-brand'
+import type { CallId, ContentBlock, MessageSource, StreamChunk, TokenUsage } from '@deepseek-ai/dsh-llm'
 
 /** Identifies one session in the store (and its persistence artifacts). */
 export type SessionId = Branded<'SessionId'>