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

src/config.ts

@@ -0,0 +1,56 @@
+/**
+ * Serializable configuration and defaults for the sidebar host half. Loader
+ * schema validation normally fills defaults; {@link resolveSidebarConfig}
+ * applies the same defaults for direct callers that bypass the Loader.
+ * @module dsh-better-sidebar/config
+ */
+
+import z from 'schemastery'
+
+/** Tunable sidebar host limits (every field optional; defaults fill in). */
+export interface SidebarConfig {
+  /** Read cap of one text file (bytes); larger files return truncated. */
+  readLimit?: number
+  /** Media route cap (bytes); larger binaries are refused. */
+  mediaLimit?: number
+  /** Explorer row bound of one level. */
+  listLimit?: number
+  /** Terminals per session. */
+  terminalsPerSession?: number
+  /** How long a disconnected terminal process survives awaiting a reconnect. */
+  reconnectGraceMs?: number
+}
+
+/** Schemastery schema for the plugin configuration. */
+export const Config: z<SidebarConfig> = z.object({
+  readLimit: z.number().step(1).min(1).default(512 * 1024),
+  mediaLimit: z.number().step(1).min(1).default(20 * 1024 * 1024),
+  listLimit: z.number().step(1).min(1).default(1000),
+  terminalsPerSession: z.number().step(1).min(1).default(3),
+  reconnectGraceMs: z.number().step(1).min(0).default(30_000),
+})
+
+/** Fully defaulted sidebar host settings. */
+export interface ResolvedSidebarConfig {
+  readLimit: number
+  mediaLimit: number
+  listLimit: number
+  terminalsPerSession: number
+  reconnectGraceMs: number
+}
+
+/**
+ * Apply direct-call defaults after Loader schema validation has normally run.
+ *
+ * @param config - Deployment-provided sidebar host settings.
+ * @returns Complete settings consumed by the host half.
+ */
+export function resolveSidebarConfig(config: SidebarConfig | undefined): ResolvedSidebarConfig {
+  return {
+    readLimit: config?.readLimit ?? 512 * 1024,
+    mediaLimit: config?.mediaLimit ?? 20 * 1024 * 1024,
+    listLimit: config?.listLimit ?? 1000,
+    terminalsPerSession: config?.terminalsPerSession ?? 3,
+    reconnectGraceMs: config?.reconnectGraceMs ?? 30_000,
+  }
+}