[Bug]: File chips for files created outside the project root fail to open: "Failed to read workspace file 'docs/X.md' in '<root>'"

Area: apps/web

Steps to reproduce:

1. Open a project rooted at a directory that is not the folder the agent works in (e.g. project root ~/Documents, agent working inside ~/Documents/<subdir>).
2. Ask the agent to create a file relative to its own cwd, e.g. docs/GROUPS_PLAN.md.
3. In the assistant's reply, click the rendered file chip for that file (message text references it as e.g. docs/GROUPS_PLAN.md:46).
4. The file preview panel errors instead of opening the file.

Expected behavior:

Clicking the chip opens the file the agent actually created (~/Documents/<subdir>/docs/GROUPS_PLAN.md) in the file preview panel.

Actual behavior:

An error toast and a broken preview panel:

Failed to read workspace file 'docs/GROUPS_PLAN.md' in '/Users/<user>/Documents'.

/Users/<user>/Documents/docs/GROUPS_PLAN.md:46

Impact: Minor bug or occasional failure

Version or commit: 0.0.34-nightly.20260825.1180 (99960383d094)

Environment: macOS 26.6.2, T3 Code desktop app 0.0.34-nightly.20260825.1180, OpenCode provider

Logs or stack traces:

[projects.readFile] ProjectReadFileError {
  cwd: "/Users/<user>/Documents",
  relativePath: "docs/GROUPS_PLAN.md",
  failure: "operation_failed",
  operation: "realpath-target",
  operationPath: "/Users/<user>/Documents/docs/GROUPS_PLAN.md",
}

Workaround: Open the file via the Files explorer instead of the chip.

Start in apps/web by tracing rendered file chips to the file preview panel and the projects.readFile operation. Reproduce the issue with different project roots and agent working directories, then verify that clicking a chip opens the file created in the agent's cwd rather than resolving it only from the project root.