docs(credentials): record the third-review contracts across READMEs, catalogs, and a new Agent Note

Both provider READMEs state what actually holds: credentials-local now
documents the physical-line editor, the read-modify-write under the
writer lock, and a Security boundary section saying plainly that the file
mode stops other OS users and not the model. sandbox-policy documents
readDenyPaths and its per-backend enforcement. The llm READMEs carry the
registration handle, pi-ai's credential-miss semantics, and DeepSeek's
same-generation snapshot; app-boot and the CLI README stop describing
$DSH_HOME/.env as an environment layer.

A new Agent Note records the round (and the prior seam note cross-links
it); the sandbox and core catalog pages gain readDenyPaths and
AdapterRegistrationHandle with their manifest entries. The headless
missing-credential snapshot re-records for the reworded guidance, pi-ai
gains the Loader-composition guard its twin already had, and the
deliberate provider symmetry is marked for the clone detector.

packages/cordis/tool-cordis/src/api-catalog.ts

@@ -405,8 +405,8 @@ export const SERVICE_API: readonly ServiceApiEntry[] = [
     summary: 'The abstract `llm` service: an adapter registry plus a streaming model-call surface, interceptable via the `llm/stream` waterfall.',
     methods: [
       {
-        signature: 'registerAdapter(providers: string[], adapter: LlmAdapter): () => void',
-        jsDoc: '/**\n * Register an adapter for the given provider routes. Throws `LlmError` with code\n * `DUPLICATE_ADAPTER` if any provider already has an adapter (all-or-nothing).\n * Disposed with the fiber.\n * @param providers - every provider route this adapter should serve.\n * @param adapter - the adapter that streams calls for those providers.\n * @returns the disposer that unregisters all of them.\n */',
+        signature: 'registerAdapter(providers: string[], adapter: LlmAdapter): AdapterRegistrationHandle',
+        jsDoc: '/**\n * Register an adapter for the given provider routes. Throws `LlmError` with code\n * `DUPLICATE_ADAPTER` if any provider already has an adapter (all-or-nothing).\n * Disposed with the fiber.\n * @param providers - every provider route this adapter should serve.\n * @param adapter - the adapter that streams calls for those providers.\n * @returns the disposer, carrying {@link AdapterRegistrationHandle.replace}.\n */',
       },
       {
         signature: 'listProviders(): LlmProviderInfo[]',
@@ -1297,7 +1297,7 @@ export const EVENT_API: readonly EventApiEntry[] = [
     name: 'credentials/updated',
     mode: 'emit',
     signature: '\'credentials/updated\'(ref: CredentialRef): void',
-    jsDoc: '/**\n * Committed change to a provider-managed credential source: a `set`, an\n * `unset`, or an external edit observed in storage. Ambient\n * process-environment changes are not observable and never emit.\n * @param ref - the reference whose stored value changed.\n * @mode emit\n */',
+    jsDoc: '/**\n * Committed change to a provider-managed credential source: a `set`, an\n * `unset`, or an external edit observed in storage. Ambient\n * process-environment changes are not observable and never emit. Listener\n * failures are contained and logged — a sync throw and an async rejection\n * alike — without changing the committed operation\'s outcome, except\n * `INVARIANT`-coded failures, which rethrow after every listener ran;\n * that rethrow reaches the emitter only from synchronous listeners, so\n * invariant checks on this event must not be async functions.\n * @param ref - the reference whose stored value changed.\n * @mode emit\n */',
     summary: 'Committed change to a provider-managed credential source: a `set`, an `unset`, or an external edit observed in storage.',
   },
   {
@@ -1521,6 +1521,10 @@ export const EVENT_API: readonly EventApiEntry[] = [
 
 /** Shapes of every exported type the SERVICE_API signatures reference (transitively), sorted by name. */
 export const TYPE_API: readonly TypeApiEntry[] = [
+  {
+    name: 'AdapterRegistrationHandle',
+    declaration: 'export interface AdapterRegistrationHandle {\n    (): void;\n    replace(providers: string[]): void;\n}',
+  },
   {
     name: 'Agent',
     declaration: 'export interface Agent {\n    readonly id: SessionId;\n    readonly options: AgentOptions;\n    readonly session: Session;\n    readonly status: AgentStatus;\n    readonly acceptsNextStep: boolean;\n    readonly ctx: Context;\n    send(message: UserMessage, options: SendOptions): void;\n    updateInbox(id: InboxItemId, action: InboxAction): InboxActionResult;\n    cancel(cause: AgentCancelCause, options?: CancelOptions): void;\n    whenIdle(): Promise<void>;\n    followup(message: UserMessage): void;\n    steer(message: UserMessage): void;\n    inject(message: UserMessage): void;\n}',
@@ -2207,7 +2211,7 @@ export const TYPE_API: readonly TypeApiEntry[] = [
   },
   {
     name: 'SandboxExecutionPolicy',
-    declaration: 'export interface SandboxExecutionPolicy {\n    mode: SandboxMode;\n    workspaceRoot: string;\n}',
+    declaration: 'export interface SandboxExecutionPolicy {\n    mode: SandboxMode;\n    workspaceRoot: string;\n    readDenyPaths?: readonly string[];\n}',
   },
   {
     name: 'SandboxMode',