feat(conformance): wire cross-feature reader pattern into docs and schema

Add reads field to UseCaseManifest, update CLAUDE.md with Q0-Q3 rules,
add ./reader subpath to AGENTS.md exports table, and cascade reader
conventions through conformance quickref, adding-a-feature guide, and
scaffolding guide. Moves gen reader from deferred to planned.

docs/guides/conformance-quickref.md

@@ -21,6 +21,7 @@ export const fooManifest = defineFeature({
       audits: ["thing.created"],
       publishes: ["foo.thing-created"],
       consumes: [],
+      reads: ["auth"], // cross-feature reader dependency
     },
   },
   realtimeChannels: [],
@@ -40,6 +41,7 @@ Field reference:
 | `useCases.<name>.audits`    | string[]          | Audit event types this use case emits via `auditLog.record({ type: "X" })`                                        |
 | `useCases.<name>.publishes` | string[]          | Cross-feature events this use case publishes via `bus.publish("X")`                                               |
 | `useCases.<name>.consumes`  | string[]          | Cross-feature events this use case consumes (via an event handler)                                                |
+| `useCases.<name>.reads`     | string[]          | Other features whose readers this use case queries (e.g. `["auth"]`)                                              |
 | `realtimeChannels`          | string[]          | Realtime channels this feature owns                                                                               |
 | `jobs`                      | string[]          | Job slugs this feature enqueues                                                                                   |
 | `requiresConsent`           | ConsentCategory[] | Consent categories feature use cases require; drives `withConsent` wrapping + `no-undeclared-consent-check`       |