docs: ROADMAP full restore + #98-143 tech debt links + archive historical DESIGN/CHANGES (#144)

docs/archive/DESIGN-0.17.0.md

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+# DESIGN-0.17.0 — Persona-KB Binding + Enterprise KB Mode
+
+## Overview
+
+Personas become **gateways** to knowledge. In enterprise deployments,
+users don't interact with KBs directly — they talk to Personas that
+have KBs attached. This is the core differentiator for enterprise use.
+
+Depends on: knowledge bases (v0.14.0), user groups (v0.16.0).
+
+**Design principle: Personas carry context, not users.** When a user
+selects a Persona with bound KBs, the KB context flows automatically —
+no manual KB selection, no toggle management, no confusion about which
+KBs are in scope. Admins curate the KB↔Persona relationships; users
+just pick a Persona.
+
+---
+
+## 1. Schema
+
+### `persona_knowledge_bases` (new join table)
+
+```sql
+CREATE TABLE persona_knowledge_bases (
+    persona_id  UUID NOT NULL REFERENCES personas(id) ON DELETE CASCADE,
+    kb_id       UUID NOT NULL REFERENCES knowledge_bases(id) ON DELETE CASCADE,
+    auto_search BOOLEAN NOT NULL DEFAULT false,
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+    PRIMARY KEY (persona_id, kb_id)
+);
+```
+
+`auto_search` controls whether the KB is searched automatically on every
+message (top-K results prepended to context) or only via explicit
+`kb_search` tool calls. Default `false` = tool-only.
+
+### `knowledge_bases.discoverable` (new column)
+
+```sql
+ALTER TABLE knowledge_bases ADD COLUMN discoverable BOOLEAN NOT NULL DEFAULT true;
+```
+
+When `false`, the KB does not appear in user-facing listings
+(`ListDiscoverableKBs`). It remains searchable through Persona bindings.
+
+### `platform_policies.kb_direct_access` (new row)
+
+Seeded as `'true'` (permissive default). When set to `'false'`, the
+channel KB popup is hidden — users access KBs exclusively through
+Persona bindings.
+
+---
+
+[... full content ...]