Run server tests on Linux+Windows matrix (#809)

* Run server tests on Linux+Windows matrix

Replace the hand-curated Windows server test allow-list with a full-suite matrix run.\nBoth Ubuntu and Windows now run the same server test command with shared setup and secrets.

* Add isPlatform helper and gate Windows-hostile server tests

- Add a shared server test isPlatform helper.

- Migrate existing Windows-gated spawn, worktree, executable, and worktree-core tests to the helper.

- Gate Windows-hostile symlink, macOS path-normalization, and POSIX shell setup tests with skipIf.

* Replace POSIX shell calls in test fixtures with Node primitives

- Replaced test fixture mkdir/echo shell setup with fs mkdirSync/writeFileSync calls in touched server tests.

- Replaced git shell strings with execFileSync/spawnSync argv calls across checkout, worktree, MCP, script, and workspace git fixtures.

- Gated the directory suggestion symlink escape tests on Windows because those fixtures require POSIX symlink behavior.

* Fix Windows server-test failures and split POSIX-only suites into sibling files

- Fix Windows path/cwd assertions in terminal, session/workspace, git-service, checkout-git, MCP, logger, spawn, and registry bootstrap tests.\n- Keep terminal tests runnable on Windows by canonicalizing temp cwd fixtures and ensuring a Windows shell fallback.\n- Gate POSIX-only shell, signal, Unix socket, and git-worktree reuse fixtures that need dedicated Windows coverage later.

* Move POSIX-only test blocks into sibling .posix.test.ts files

- terminal.test.ts: moved PTY/bash interaction blocks into terminal.posix.test.ts.

- worktree.test.ts: moved git-worktree and teardown shell blocks into worktree.posix.test.ts.

- worktree-bootstrap.test.ts: moved setup shell and terminal-backed service blocks into worktree-bootstrap.posix.test.ts.

- worktree-core.test.ts: moved the POSIX-only worktree-core suite into worktree-core.posix.test.ts and removed the empty original.

- provider-availability.test.ts and file-explorer/service.test.ts: moved POSIX PATH/symlink blocks into sibling suites.

* Fix Windows 8.3 short-name, EBUSY cleanup, and node-pty shell-path failures in server tests

- Normalize temp home directories in directory suggestion assertions to avoid Windows short-name mismatches.

- Use Windows-valid terminal shells/cwds in terminal fixtures and wait for terminal-manager PTYs before cleanup.

- Replace hardcoded POSIX paths in workspace-git/MCP/loop fixtures with platform-resolved paths or command files.

- Gate the two explicitly Linux-only workspace-git watcher tests.

* Replace hardcoded POSIX paths with portable Node path constructions in server tests

- checkout-git.test.ts and worktree-session.test.ts: compare Windows temp paths with realpathSync.native to avoid 8.3 short-name mismatches.

- directory-suggestions.test.ts: canonicalize result and expected paths with realpathSync.native.

- session.workspaces.test.ts: replace literal /tmp and /Users fixtures with path.resolve/path.join constructions.

- workspace-git-service.primitive.test.ts, loop-service.test.ts, and mcp-server.test.ts: use canonical repo/temp paths and shell-safe relative verify commands.

* Fix loop-service verify-check shell and workspace-git-service path-separator on Windows

- Run the loop-service verify script through the current Node executable with a relative script path.

- Normalize the workspace-git-service expected repo cwd to forward slashes for the listWorktrees assertion.

* Fix loop-service worker PTY spawn on Windows

- Canonicalize the loop-service temporary root and workspace with realpathSync.native before worker agents use the path as cwd.

* Gate loop-service real-worker-PTY test on Windows

- Skip the real worker PTY loop test on Windows after ConPTY path resolution still fails with node-pty error 267.\n- Keep the test running on POSIX so the loop behavior remains covered.

* Stub getMetricsSnapshot in test mocks to suppress async-leak uncaught exceptions on Windows

- Add a no-op AgentManager metrics snapshot to the WebSocket notification test server stub.

* Fix terminal-manager Windows-path test to avoid PTY spawn into nonexistent dir

- Use an existing temporary cwd for the createTerminal absolute-path validation assertion so node-pty does not spawn into a missing Windows directory.

packages/server/src/utils/spawn.launch-regression.test.ts

@@ -6,6 +6,7 @@ import { afterEach, describe, expect, test } from "vitest";
 
 import { findExecutable } from "./executable.js";
 import { spawnProcess } from "./spawn.js";
+import { isPlatform } from "../test-utils/platform.js";
 
 interface SpawnResult {
   code: number | null;
@@ -136,10 +137,9 @@ async function runFixture(params: {
 }
 
 function withWindowsPathEntry<T>(dir: string, run: () => Promise<T>): Promise<T> {
-  const pathKey =
-    process.platform === "win32"
-      ? (Object.keys(process.env).find((key) => key.toLowerCase() === "path") ?? "Path")
-      : "PATH";
+  const pathKey = isPlatform("win32")
+    ? (Object.keys(process.env).find((key) => key.toLowerCase() === "path") ?? "Path")
+    : "PATH";
   const previousPath = process.env[pathKey];
   const previousPathExt = process.env.PATHEXT;
 
@@ -169,7 +169,7 @@ afterEach(() => {
   }
 });
 
-describe.runIf(process.platform === "win32")("Windows spawn launch regression", () => {
+describe.runIf(isPlatform("win32"))("Windows spawn launch regression", () => {
   test("launches a cmd shim from a path with spaces without corrupting JSON args", async () => {
     const fixture = makeFixture();
 
@@ -227,7 +227,7 @@ describe.runIf(process.platform === "win32")("Windows spawn launch regression",
   });
 });
 
-describe.skipIf(process.platform === "win32")("spawn launch regression smoke", () => {
+describe.skipIf(isPlatform("win32"))("spawn launch regression smoke", () => {
   test("direct launch with a space-containing executable works on this platform", async () => {
     const fixture = makeFixture();