feat: per-session store + configurable host limits; fix divider drag runaway

- state: side-store per conversation, injected as a prop instead of a module singleton
- host: schemastery Config (read/media/list/terminal limits) resolved from cordis config
- shape: types/exports/peerDependencies for the web profile + plugin-shape spec
- fix: split divider emits incremental deltas so drags track the cursor 1:1
- docs: README refresh

tests/plugin-shape.spec.ts

@@ -0,0 +1,38 @@
+import { describe, expect, it } from 'vitest'
+import Loader from '@cordisjs/plugin-loader'
+import * as sidebar from '../src/index.ts'
+
+/**
+ * Run the real namespace export through `Loader.unwrapExports`; a stray
+ * default would discard `name`, `inject`, `Config`, and `apply`. Same guard
+ * the official plugin repos ship (dsh-external/turtle-ui,
+ * packages/ui/jsonrpc).
+ */
+describe('dsh-better-sidebar plugin export shape', () => {
+  it('has the namespace-plugin export shape (no stray default) so the Loader keeps name/inject/Config/apply', () => {
+    expect('default' in sidebar).toBe(false)
+    expect(typeof sidebar.apply).toBe('function')
+
+    const loader = Object.create(Loader.prototype) as Loader
+    const unwrapped = loader.unwrapExports(sidebar) as Record<string, unknown>
+    expect(unwrapped).toBe(sidebar)
+    expect(unwrapped.name).toBe('dsh-better-sidebar')
+    expect(unwrapped.inject).toEqual(['httpServer', 'sessions', 'loader'])
+    expect(unwrapped.Config).toBeDefined()
+    expect(typeof unwrapped.apply).toBe('function')
+  })
+
+  it('exports the schemastery Config with the documented tunable fields', () => {
+    const schema = sidebar.Config
+    expect(schema).toBeDefined()
+    // The resolved defaults mirror the pre-config constants.
+    const resolved = (schema as unknown as {
+      (input: Record<string, unknown> | undefined): Record<string, unknown>
+    })(undefined)
+    expect(resolved.readLimit).toBe(512 * 1024)
+    expect(resolved.mediaLimit).toBe(20 * 1024 * 1024)
+    expect(resolved.listLimit).toBe(1000)
+    expect(resolved.terminalsPerSession).toBe(3)
+    expect(resolved.reconnectGraceMs).toBe(30_000)
+  })
+})