refactor(plan): remove generic mode abstraction

packages/plan/plan-mode/src/invariant.ts

@@ -0,0 +1,43 @@
+/** Package-owned durable plan-mode invariants. @module @deepseek-ai/dsh-plan-mode/invariant */
+
+import type { Context } from 'cordis'
+import type { Session, SessionEvent } from '@deepseek-ai/dsh-session'
+import type { InvariantFailure, InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-plan-mode'
+
+/** Cordis companion plugin name. */
+export const name = 'plan-mode-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/** Validate one `plan/mode` payload before it reaches the durable log. */
+function validateEvent(event: SessionEvent, fail: InvariantFailure): void {
+  if (event.type !== 'plan/mode') return
+  const active = (event.data as { active?: unknown }).active
+  if (typeof active !== 'boolean') {
+    fail(`plan/mode carries invalid active state ${JSON.stringify(active)}; expected a boolean`)
+  }
+}
+
+/* jscpd:ignore-start -- package companions share replay and dispatch plumbing */
+/** Install validation for loaded and newly appended plan-mode state. */
+const install: InvariantInstaller = Object.assign((ctx: Context, fail: InvariantFailure) => {
+  for (const session of ctx.sessions.list()) {
+    for (const event of session.events) validateEvent(event, fail)
+  }
+  ctx.on('internal/dispatch', (_mode, eventName, args) => {
+    if (eventName !== 'session/event') return
+    const event = (args as [Session, SessionEvent])[1]
+    validateEvent(event, fail)
+  }, { global: true })
+}, { inject: ['sessions'] })
+/* jscpd:ignore-end */
+
+/**
+ * Register the plan-mode invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))