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/session-reset-strategy.ts

@@ -0,0 +1,65 @@
+import type { PluginInput } from "@opencode-ai/plugin"
+import { getServerBasicAuthHeader } from "../../shared/opencode-server-auth"
+import { getServerBaseUrl, log } from "../../shared"
+
+export async function createIterationSession(
+  ctx: PluginInput,
+  parentSessionID: string,
+  directory: string,
+): Promise<string | null> {
+  const createResult = await ctx.client.session.create({
+    body: {
+      parentID: parentSessionID,
+      title: "Ralph Loop Iteration",
+    },
+    query: { directory },
+  })
+
+  if (createResult.error || !createResult.data?.id) {
+    log("[ralph-loop] Failed to create iteration session", {
+      parentSessionID,
+      error: String(createResult.error ?? "No session ID returned"),
+    })
+    return null
+  }
+
+  return createResult.data.id
+}
+
+export async function selectSessionInTui(
+  client: PluginInput["client"],
+  sessionID: string,
+): Promise<boolean> {
+  const baseUrl = getServerBaseUrl(client)
+  const authorization = getServerBasicAuthHeader()
+
+  if (!baseUrl || !authorization) {
+    return false
+  }
+
+  const response = await fetch(`${baseUrl}/tui/select-session`, {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/json",
+      Authorization: authorization,
+    },
+    body: JSON.stringify({ sessionID }),
+    signal: AbortSignal.timeout(5000),
+  }).catch((error: unknown) => {
+    log("[ralph-loop] Failed to select session in TUI", {
+      sessionID,
+      error: String(error),
+    })
+    return null
+  })
+
+  if (!response?.ok) {
+    log("[ralph-loop] TUI session select request failed", {
+      sessionID,
+      status: response?.status,
+    })
+    return false
+  }
+
+  return true
+}