feat(sisyphus): add foundation schemas for tasks and swarm (Wave 1)

- Add SisyphusTasksConfig and SisyphusSwarmConfig to schema.ts
- Create Task JSON schema with Zod validation
- Create Mailbox IPC protocol message schemas
- Add storage utilities with Claude Code path compatibility
- 25 tests passing

src/features/sisyphus-tasks/storage.ts

@@ -0,0 +1,82 @@
+import { join, dirname } from "path"
+import { existsSync, mkdirSync, readFileSync, writeFileSync, renameSync, unlinkSync } from "fs"
+import { homedir } from "os"
+import type { z } from "zod"
+import type { OhMyOpenCodeConfig } from "../../config/schema"
+
+export function getTaskDir(listId: string, config: Partial<OhMyOpenCodeConfig>): string {
+  const tasksConfig = config.sisyphus?.tasks
+
+  if (tasksConfig?.claude_code_compat) {
+    return join(homedir(), ".cache", "claude-code", "tasks", listId)
+  }
+
+  const storagePath = tasksConfig?.storage_path ?? ".sisyphus/tasks"
+  return join(process.cwd(), storagePath, listId)
+}
+
+export function getTaskPath(listId: string, taskId: string, config: Partial<OhMyOpenCodeConfig>): string {
+  return join(getTaskDir(listId, config), `${taskId}.json`)
+}
+
+export function getTeamDir(teamName: string, config: Partial<OhMyOpenCodeConfig>): string {
+  const swarmConfig = config.sisyphus?.swarm
+
+  if (swarmConfig?.storage_path?.includes("claude")) {
+    return join(homedir(), ".claude", "teams", teamName)
+  }
+
+  const storagePath = swarmConfig?.storage_path ?? ".sisyphus/teams"
+  return join(process.cwd(), storagePath, teamName)
+}
+
+export function getInboxPath(teamName: string, agentName: string, config: Partial<OhMyOpenCodeConfig>): string {
+  return join(getTeamDir(teamName, config), "inboxes", `${agentName}.json`)
+}
+
+export function ensureDir(dirPath: string): void {
+  if (!existsSync(dirPath)) {
+    mkdirSync(dirPath, { recursive: true })
+  }
+}
+
+export function readJsonSafe<T>(filePath: string, schema: z.ZodType<T>): T | null {
+  try {
+    if (!existsSync(filePath)) {
+      return null
+    }
+
+    const content = readFileSync(filePath, "utf-8")
+    const parsed = JSON.parse(content)
+    const result = schema.safeParse(parsed)
+
+    if (!result.success) {
+      return null
+    }
+
+    return result.data
+  } catch {
+    return null
+  }
+}
+
+export function writeJsonAtomic(filePath: string, data: unknown): void {
+  const dir = dirname(filePath)
+  ensureDir(dir)
+
+  const tempPath = `${filePath}.tmp.${Date.now()}`
+
+  try {
+    writeFileSync(tempPath, JSON.stringify(data, null, 2), "utf-8")
+    renameSync(tempPath, filePath)
+  } catch (error) {
+    try {
+      if (existsSync(tempPath)) {
+        unlinkSync(tempPath)
+      }
+    } catch {
+      // Ignore cleanup errors
+    }
+    throw error
+  }
+}