core: move cross-spawn-spawner from opencode to core package

Moved the cross-spawn-spawner module from packages/opencode to packages/core
to enable code sharing across the monorepo. This consolidates the process
spawning infrastructure into the core package so other packages can use
cross-platform child process spawning without duplicating the implementation.

Updated all import statements across the codebase to reference the new
location (@opencode-ai/core/effect/cross-spawn-spawner). Removed the
local copy from the opencode package along with its tests.

packages/opencode/test/project/project.test.ts

@@ -10,7 +10,7 @@ import { Effect, Layer, Stream } from "effect"
 import { ChildProcess, ChildProcessSpawner } from "effect/unstable/process"
 import { NodePath } from "@effect/platform-node"
 import { AppFileSystem } from "@opencode-ai/core/filesystem"
-import * as CrossSpawnSpawner from "../../src/effect/cross-spawn-spawner"
+import { CrossSpawnSpawner } from "@opencode-ai/core/effect/cross-spawn-spawner"
 
 void Log.init({ print: false })
 

packages/opencode/test/project/worktree-remove.test.ts

@@ -3,7 +3,7 @@ import { describe, expect } from "bun:test"
 import * as fs from "fs/promises"
 import path from "path"
 import { Effect, Layer } from "effect"
-import * as CrossSpawnSpawner from "@/effect/cross-spawn-spawner"
+import { CrossSpawnSpawner } from "@opencode-ai/core/effect/cross-spawn-spawner"
 import { Worktree } from "../../src/worktree"
 import { provideTmpdirInstance } from "../fixture/fixture"
 import { testEffect } from "../lib/effect"

packages/opencode/test/project/worktree.test.ts

@@ -3,7 +3,7 @@ import { afterEach, describe, expect } from "bun:test"
 import * as fs from "fs/promises"
 import path from "path"
 import { Cause, Effect, Exit, Layer } from "effect"
-import * as CrossSpawnSpawner from "@/effect/cross-spawn-spawner"
+import { CrossSpawnSpawner } from "@opencode-ai/core/effect/cross-spawn-spawner"
 import { Instance } from "../../src/project/instance"
 import { Worktree } from "../../src/worktree"
 import { provideInstance, provideTmpdirInstance } from "../fixture/fixture"