fix: clean up OpenCode streams and allow external working directories

Completed OpenCode requests left their event streams open across repeated and
parallel conversations. Each request now closes its own subscription on exit
without cancelling peer sessions, and cancellation preserves its original cause.

Direct-model Execute commands no longer restrict cwd to the workspace. Absolute
paths, parent-relative paths, and symlinks to external directories are accepted.
The workspace remains the default and relative-path base; Ask stays read-only,
and local execution binding, directory validation, and process cleanup remain.

Add real OpenCode lifecycle and real Shell tool-loop regressions, plus matching
feature documentation. Focused checks: 182 passed, 1 skipped; typecheck and lint
passed. Full shared-worktree suite: 3542 passed, 57 skipped, 1 unrelated sidebar
heading failure, reproduced separately and documented.

Release note: 修复 OpenCode 连续及并行对话结束后事件连接未释放的问题；直连模型 Execute 命令现在可直接指定工作区外的绝对路径、相对路径或符号链接目录，Ask 只读边界保持不变。

src/main/agent/direct-model-process-service.ts

@@ -28,7 +28,15 @@ export const DIRECT_MODEL_PROCESS_TRUNCATION_MARKER =
 export const processExecuteInputSchema = z
   .object({
     command: z.string().trim().min(1).max(100_000),
-    cwd: z.string().trim().min(1).max(4_096).optional(),
+    cwd: z
+      .string()
+      .trim()
+      .min(1)
+      .max(4_096)
+      .describe(
+        '工作目录，可使用绝对路径或相对于当前工作区的路径；省略时使用工作区根目录，也可选择工作区外目录。'
+      )
+      .optional(),
     timeoutMs: z
       .number()
       .int()
@@ -350,10 +358,6 @@ async function resolveWorkingDirectory(
   if (input.cwd?.includes('\0')) {
     throw new Error('工作目录包含无效字符')
   }
-  if (input.cwd && isAbsolute(input.cwd)) {
-    throw new Error('工作目录必须相对于工作区')
-  }
-
   const initialIdentity = await workspace.getIdentity()
   if (initialIdentity.kind !== 'local') {
     throw new Error('本机进程不能在远程工作区中运行')
@@ -365,23 +369,8 @@ async function resolveWorkingDirectory(
     throw new Error('项目工作区不是目录')
   }
   const candidatePath = resolve(canonicalRoot, input.cwd ?? '.')
-  const lexicalDifference = relative(canonicalRoot, candidatePath)
-  if (
-    lexicalDifference === '..' ||
-    lexicalDifference.startsWith(`..${sep}`) ||
-    isAbsolute(lexicalDifference)
-  ) {
-    throw new Error('工作目录不能超出项目工作区')
-  }
   const canonicalPath = await realpath(candidatePath)
   const canonicalDifference = relative(canonicalRoot, canonicalPath)
-  if (
-    canonicalDifference === '..' ||
-    canonicalDifference.startsWith(`..${sep}`) ||
-    isAbsolute(canonicalDifference)
-  ) {
-    throw new Error('工作目录不能通过符号链接超出项目工作区')
-  }
   if (!(await stat(canonicalPath)).isDirectory()) {
     throw new Error('工作目录不是目录')
   }
@@ -397,7 +386,12 @@ async function resolveWorkingDirectory(
   }
   return {
     canonicalPath,
-    displayPath: canonicalDifference || '.'
+    displayPath:
+      canonicalDifference === '..' ||
+      canonicalDifference.startsWith(`..${sep}`) ||
+      isAbsolute(canonicalDifference)
+        ? canonicalPath
+        : canonicalDifference || '.'
   }
 }