bug: C++ syntax highlighting is missing for common file extensions

[satouriko]

Description

The workspace editor recognizes .cpp and .hpp files as C++, but other common C++ extensions are not assigned a language. Files such as .cc, .cxx, .hh, and .hxx therefore open without C++ syntax highlighting even though the frontend already supports the cpp language identifier.

Steps to reproduce

1. Open a workspace containing a C++ file named with one of these extensions: .cc, .cxx, .hh, or .hxx.
2. Open the file in the workspace editor.
3. Observe that C++ syntax highlighting is not applied.

Expected behavior

These common C++ source and header extensions should use the existing C++ syntax highlighting support.

Proposed fix

Add .cc, .cxx, .hh, and .hxx to TEXT_EXTENSIONS and map them to cpp in _detect_language.

A minimal implementation based on the current main branch is available here:

satouriko@1f8441c

It has been checked with:

• ruff 0.15.16 format --check cptr/routers/workspace.py
• python -m py_compile cptr/routers/workspace.py
• focused checks confirming that each added extension resolves to cpp

[owui-terminator]

⚠️ Missing Issue Title Prefix

@satouriko, your issue title is missing a categorising prefix (e.g. bug:, feat:, docs:).

Please update the title to lead with one of:

• bug: bug report or error
• feat: feature request or enhancement
• docs: documentation issue
• question: usage question
• help: support request

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