fix(lsp/process): prefer PATHEXT extensions over extensionless name (#4262)

[YOMXXX]

Closes code-yeongyu/oh-my-openagent#4262.

Root cause

getWindowsPathExtensions returned the candidate extension list with an empty string at the front:

```ts
return [...new Set(["", ...extensions, ".exe", ".cmd", ".bat"])];
```

On Windows, when an LSP server ships both an extensionless shebang script and a `.bat`/`.cmd` companion — `jdtls` is the canonical case — `resolveWindowsCommand`'s inner loop tried the empty string first, matched the extensionless file via `existsSync`, and returned its full path.

`isWindowsShellShim` then returned `false` (the resolved path doesn't end with `.bat`/`.cmd`), so Node spawned the extensionless Python script directly. Windows can't honor shebangs, so spawn failed with `UV_ENOENT` (`-4058`) and the language server never came up.

Fix

Move the empty string to the end of the array so PATHEXT extensions get checked first — matching `cmd.exe`'s actual lookup order:

```ts
return [...new Set([...extensions, ".exe", ".cmd", ".bat", ""])];
```

Now `jdtls.bat` wins, `isWindowsShellShim` returns true, and the wrapper goes through `cmd.exe /d /s /c jdtls.bat ...` — which is what jdtls needs to set `JAVA_HOME` correctly.

Test plan

• New regression in `test/process.test.ts`: drops both files (`jdtls` extensionless shebang + `jdtls.bat` wrapper) into a tmp dir and asserts `createSpawnCommand(["jdtls", ...], "win32", ...)` returns `cmd.exe /d /s /c /jdtls.bat`.
• RED-GREEN verified locally: revert the array reordering and the new test fails with the extensionless script selected; restore and 28/28 tests pass.

---

Summary by cubic

Prefer Windows PATHEXT extensions over extensionless names when resolving LSP binaries. Ensures jdtls and similar servers run via their .bat/.cmd wrapper instead of the shebang script, avoiding UV_ENOENT.

• Bug Fixes
  • Reordered getWindowsPathExtensions to try PATHEXT first and the empty string last, matching cmd.exe lookup; prevents spawning extensionless scripts.
  • Added a regression test asserting createSpawnCommand(["jdtls", "--stdio"], "win32", ...) resolves to cmd.exe /d /s /c jdtls.bat.

^{Written for commit 4023034. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}

[YOMXXX]

Cross-reference: this PR is part of a roadmap covering 12 PRs across both oh-my-openagent and this submodule. See the rollup at code-yeongyu/oh-my-openagent#4293 — it groups bug fixes, regression locks, and new features with a suggested review order.

Direct link: code-yeongyu/oh-my-openagent#4293