Add agent memory: linked note store, MCP server, recall hook, and graph UI

The distilled knowledge layer over the raw log/transcript history, inspired by
TencentDB-Agent-Memory's memory-hub model, adapted to handler's invariants
(state lives only in the database; workers stay stateless and disposable):

- memory_notes + memory_links tables (migration 0014) with a portable DAL:
  scoped listing/search (project + global), idempotent linking, and a one-read
  graph. Deleting an agent nulls attribution but keeps its notes; deleting a
  project removes its notes and edges, leaving global knowledge intact.
- /memory API routes: reads on the normal token, note/link authoring on the
  admin token, plus GET /memory/graph for the dashboard.
- Bundled handler-memory MCP server (python -m handler.mcpserver), a
  dependency-free stdio JSON-RPC implementation injected into every launch's
  --mcp-config ahead of the DB connectors and allowlisted in generated
  settings, exposing memory_search / memory_get / memory_save / memory_link.
  Identity and DATABASE_URL arrive via the spawn env, same as hooks.
- SessionStart recall hook: injects the most recent notes in scope as
  additional context at session start, best-effort, never blocking.
- Memory page in the web UI: a hand-rolled force-directed SVG graph of the
  note web (colored by kind, hover highlights, click-through details), plus
  note/link authoring — the app's first visualization, no chart dependency.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WYqkoYPX8NAo1V2KyXr1pk

frontend/lib/api.ts

@@ -209,6 +209,37 @@ export interface ClaudePermissions {
   base_allow: string[];
 }
 
+/* ---- agent memory (the Memory page's note graph) ---- */
+
+export type NoteKind = "fact" | "decision" | "gotcha" | "runbook";
+
+export interface MemoryNote {
+  id: number;
+  project_id?: string | null; // null = global note
+  agent_id?: number | null; // authoring agent; null = operator-authored
+  title: string;
+  body: string;
+  kind: string;
+  tags?: string[] | null;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface MemoryLink {
+  id: number;
+  src_note_id: number;
+  dst_note_id: number;
+  relation: string;
+  created_by_agent_id?: number | null;
+  created_at: string;
+}
+
+/* Everything the graph view draws, in one response (GET /memory/graph). */
+export interface MemoryGraph {
+  notes: MemoryNote[];
+  links: MemoryLink[];
+}
+
 export interface SharedContext {
   key: string;
   value: string;

frontend/lib/nav.ts

@@ -18,6 +18,7 @@ export const NAV_ROUTES: NavRoute[] = [
   { key: "servers", href: "/servers", label: "Git Servers" },
   { key: "activity", href: "/activity", label: "Activity" },
   { key: "shared", href: "/shared", label: "Shared" },
+  { key: "memory", href: "/memory", label: "Memory" },
   { key: "claude", href: "/claude", label: "Claude" },
 ];