feat(ralph-loop): add strategy option for fresh context per iteration

Closes #1901

Add 'default_strategy' config option (default: 'continue') to control whether ralph-loop creates a new session per iteration ('reset') or keeps the same session ('continue'). The 'reset' strategy keeps the model in the smart zone by starting with fresh context for each iteration.

Supports --strategy flag for per-command override.

src/hooks/ralph-loop/iteration-continuation.ts

@@ -0,0 +1,63 @@
+import type { PluginInput } from "@opencode-ai/plugin"
+import type { RalphLoopState } from "./types"
+import { log } from "../../shared/logger"
+import { HOOK_NAME } from "./constants"
+import { buildContinuationPrompt } from "./continuation-prompt-builder"
+import { injectContinuationPrompt } from "./continuation-prompt-injector"
+import { createIterationSession, selectSessionInTui } from "./session-reset-strategy"
+
+type ContinuationOptions = {
+  directory: string
+  apiTimeoutMs: number
+  previousSessionID: string
+  loopState: {
+    setSessionID: (sessionID: string) => RalphLoopState | null
+  }
+}
+
+export async function continueIteration(
+  ctx: PluginInput,
+  state: RalphLoopState,
+  options: ContinuationOptions,
+): Promise<void> {
+  const strategy = state.strategy ?? "continue"
+  const continuationPrompt = buildContinuationPrompt(state)
+
+  if (strategy === "reset") {
+    const newSessionID = await createIterationSession(
+      ctx,
+      options.previousSessionID,
+      options.directory,
+    )
+    if (!newSessionID) {
+      return
+    }
+
+    const boundState = options.loopState.setSessionID(newSessionID)
+    if (!boundState) {
+      log(`[${HOOK_NAME}] Failed to bind loop state to new session`, {
+        previousSessionID: options.previousSessionID,
+        newSessionID,
+      })
+      return
+    }
+
+    await injectContinuationPrompt(ctx, {
+      sessionID: newSessionID,
+      inheritFromSessionID: options.previousSessionID,
+      prompt: continuationPrompt,
+      directory: options.directory,
+      apiTimeoutMs: options.apiTimeoutMs,
+    })
+
+    await selectSessionInTui(ctx.client, newSessionID)
+    return
+  }
+
+  await injectContinuationPrompt(ctx, {
+    sessionID: options.previousSessionID,
+    prompt: continuationPrompt,
+    directory: options.directory,
+    apiTimeoutMs: options.apiTimeoutMs,
+  })
+}