Add Reader Bridge capture contract

docs/reader-bridge.md

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+# BearBrowser Reader Bridge
+
+BearBrowser is the capture and provenance surface for the SocioProphet Feed Intelligence reader. It must not duplicate the `SocioProphet/socioprophet/socioprophet-web/client-vue` reader UI. Its job is to discover, capture, extract, and emit governed browser evidence that downstream SocioProphet surfaces can replay.
+
+## Scope
+
+BearBrowser owns:
+
+- feed discovery from page metadata and explicit subscription links;
+- page capture initiated by a human or governed agent session;
+- canonical URL, source URL, title, timestamp, and content-hash extraction;
+- provenance emission for browser-mediated evidence;
+- policy-mediated handoff to the SocioProphet Feed Intelligence reader.
+
+BearBrowser does not own:
+
+- the full reader UI;
+- SlashTopics governance scope definition;
+- New Hope membrane admission decisions;
+- MemoryMesh recall or writeback;
+- MeshRush graph traversal;
+- ActivityPub publication.
+
+## Event vocabulary
+
+The initial reader bridge emits these canonical browser event classes:
+
+- `browser.feed.discovered`
+- `browser.feed.subscribe_requested`
+- `browser.page.captured`
+- `browser.item.extracted`
+- `browser.provenance.attached`
+- `browser.reader.handoff_requested`
+- `browser.reader.handoff_completed`
+- `browser.reader.handoff_rejected`
+
+Every event must include:
+
+- event id;
+- event type;
+- created timestamp;
+- browser profile class;
+- session authority reference when an agent session is active;
+- source URL;
+- canonical URL when available;
+- content hash or extraction hash;
+- storage policy request;
+- policy decision reference when available;
+- downstream reader handoff reference when emitted.
+
+## Capability model
+
+BearBrowser advertises reader bridge capability classes to the SourceOS control plane and AgentPlane:
+
+```yaml
+capabilities:
+  - browser.feed.discover
+  - browser.feed.subscribeRequest
+  - browser.page.capture
+  - browser.item.extract
+  - browser.reader.handoff
+  - browser.provenance
+```
+
+These capabilities are control mechanisms, not authority grants. Authority still comes from PolicyFabric, AgentPlane session scope, and SourceOS service policy.
+
+## Handoff contract
+
+The handoff target is the canonical SocioProphet Vue reader shell:
+
+```text
+SocioProphet/socioprophet/socioprophet-web/client-vue
+```
+
+The handoff payload is intentionally small:
+
+```yaml
+ReaderHandoff:
+  sourceUrl: string
+  canonicalUrl: string?
+  title: string?
+  excerpt: string?
+  contentHash: string
+  capturedAt: string
+  browserProfileClass: human | agent | terminal
+  storagePolicyRequest: localOnly | localFirstSync | hostedPrivate | hostedPublic | externalAdapter
+  evidenceRefs: string[]
+```
+
+The downstream reader is responsible for SlashTopics scope resolution, New Hope membrane evaluation, MemoryMesh posture, MeshRush graph views, and derived publication.
+
+## Acceptance criteria
+
+- Browser feed discovery can produce `browser.feed.discovered` without subscribing.
+- Browser page capture can produce `browser.page.captured` without publishing.
+- Reader handoff carries evidence references and storage policy request.
+- Agent sessions cannot invoke reader handoff unless policy permits it.
+- No browser bridge event implies ActivityPub publication or MemoryMesh writeback by itself.