Windows: project-local drive-less paths fail tool boundary checks #22799

Description

On Windows, project-local paths that lose their drive letter at tool boundaries can be handled inconsistently.

A path like C:\repo\src\file.ts can arrive as /repo/src/file.ts or \\repo\\src\\file.ts and be treated as external or outside the project even though it is on the current drive and inside the repo. This affects real tool boundaries such as read, write, edit, lsp, and external_directory checks.

The same investigation also exposed a file-backed plugin/theme metadata problem on Windows: if the file contents change without the mtime changing, refresh/install can keep using stale metadata.

Plugins

None required for the path bug.

OpenCode version

dev at c8af8f96c during investigation. Fix branch: fix/windows-plugin-loader-ci (57518bd9b).

Steps to reproduce

1. On Windows, start in a project directory.
2. Pass a project-local file through a tool boundary using a drive-less rooted path form such as /repo/src/file.ts.
3. Observe that the path can be treated as external or outside the project even though it is inside the current repo.
4. For the plugin/theme symptom, use a file-backed plugin or theme, change the file contents without changing mtime, and trigger refresh/install again.
5. Observe that the update can be missed and stale metadata can continue to be used.

Screenshot and/or share link

N/A

Operating System

Windows 11, also reproduced in Windows GitHub Actions.

Terminal

Windows Terminal locally, GitHub Actions in CI.

Related Windows-path context: #17780, #22189, #16126. Related plugin/theme context: #14847, #22119, #16559.