Bug: display_file tool produces doubled/invalid file paths in UI

Bug: display_file tool produces doubled/invalid file paths in UI

Summary

The display_file tool always returns full_path as an absolute path (e.g. C:\Users\....\Documents\GIT\scratchpad\file.md). The cptr UI then concatenates workspace + full_path, producing a doubled, invalid path like:

C:\Users\...\Documents\GIT/C:\Users\...\Documents\GIT\scratchpad\file.md

This makes file links from display_file unclickable/broken in the UI.

Environment

• cptr version: 0.9.21
• OS: Windows 11
• Architecture: AMD64
• Workspace path: C:\Users\...\Documents\GIT

Reproduction

Call display_file with any relative path, e.g.:

display_file(path="scratchpad/test.md")

Tool response (JSON):

{
  "type": "file",
  "path": "scratchpad\\test.md",
  "full_path": "C:\\Users\\....\\Documents\\GIT\\scratchpad\\test.md",
  "workspace": "C:\\Users\\.....\\Documents\\GIT",
  "name": "test.md",
  "size": 7467,
  "mime_type": "text/markdown",
  "kind": "markdown"
}

UI rendering (broken):

The UI displays a link/path constructed as {workspace}/{full_path}:

C:\Users\....\Documents\GIT/C:\Users\....\Documents\GIT\scratchpad\test.md

This path is invalid — it duplicates the workspace root prefix.

Tested Variants

All of these produce the same doubled-path result in the UI:

Input path	Tool full_path output	UI renders
scratchpad/test.md	C:\Users\...\GIT\scratchpad\test.md	C:\Users\...\GIT/C:\Users\...\GIT\scratchpad\test.md
./scratchpad/test.md	C:\Users\...\GIT\scratchpad\test.md	C:\Users\...\GIT/C:\Users\...\GIT\scratchpad\test.md
test.md (root)	C:\Users\...\GIT\test.md	C:\Users\...\GIT/C:\Users\...\GIT\test.md
C:\Users\...\test.md	C:\Users\...\GIT\scratchpad\test.md	C:\Users\...\GIT/C:\Users\...\GIT\scratchpad\test.md
/scratchpad/test.md	(rejected: "Path traversal rejected")	N/A
/test.md	(rejected: "Path traversal rejected")	N/A

Root Cause

The display_file tool resolves the input path to an absolute path and stores it in full_path. The UI then constructs the display path as {workspace}/{full_path}. Since full_path already starts with the workspace path, the workspace prefix is duplicated.

Expected Behavior

The UI should use either:

1. full_path directly (it's already absolute), or
2. {workspace}/{path} (joining workspace with the relative path)

...but not {workspace}/{full_path}.

Start at the display_file entry point and trace the UI rendering that constructs links from workspace, path, and full_path. Reproduce the Windows case with a relative path, then verify that file links no longer duplicate the workspace prefix and remain clickable.