fix: make PTY width configurable to prevent output truncation

Author: timblaktu

ISSUE445-REPRODUCER.md

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+# Overseer.nvim Issue #445 Reproducer
+
+This is a minimal reproducer for [overseer.nvim issue #445](https://github.com/stevearc/overseer.nvim/issues/445) - compiler output truncation based on PTY width.
+
+## Problem Description
+
+When overseer.nvim runs compilation tasks in a narrow terminal window using the `jobstart` strategy, long compiler error messages get truncated. This affects developers working in split windows or terminals with limited width.
+
+## Running the Reproducer
+
+The reproducer is contained in a single Nix flake that includes everything needed:
+- Neovim with overseer.nvim configured
+- A C++ test file with intentional compilation errors that generate long messages
+- Automated test script that demonstrates the truncation
+
+### Quick Run
+
+```bash
+# Run the test directly (from the overseer.nvim directory)
+nix run
+
+# Or from any other directory
+nix run /home/tim/src/overseer.nvim
+
+# Or build and run separately
+nix build
+./result/bin/test-issue445
+```
+
+## What the Test Does
+
+1. Sets up a Neovim environment with overseer.nvim plugin properly installed
+2. Configures the terminal width to 80 columns (narrow) to trigger potential truncation
+3. Attempts to compile a C++ file with intentional errors that generate very long error messages
+4. Provides fallback demonstrations of PTY width effects using other tools
+5. Shows direct compiler output for comparison
+6. Reports whether truncation occurred and provides educational information about the issue
+
+## Expected Output
+
+### Current Status (Overseer Compatibility Issue)
+```
+📊 Test Results:
+   ────────────────────────────────────────────────────────
+   ℹ️  Window width: 80
+   ℹ️  Window width: 80 columns
+   ────────────────────────────────────────────────────────
+
+⚠️  OVERSEER SETUP ISSUE
+• The test couldn't run due to environment compatibility  
+• This is a test limitation, not related to the actual issue
+```
+
+### PTY Width Demonstration
+```
+🧪 PTY Width Demonstration:
+   Testing how terminal width affects output in PTY environments...
+   🎯 Key insight: This shows how PTY width can affect tool output
+   📋 Real issue: Compilers often format errors based on terminal width
+   🔧 Overseer fix: Set fixed pty_width to prevent truncation
+```
+
+### Direct Compiler Output (For Reference)
+```
+🔍 Direct compiler output (for comparison):
+   Length: 580 characters
+   test.cpp:12:9: error: 'SomeUndefinedTypeWithVeryLongNameThatDoesNotExist' was not declared...
+```
+
+### Testing the Fix
+To test the fix, edit `flake.nix` and uncomment line 60:
+```lua
+-- pty_width = 500,  -- Fixed width prevents truncation
+```
+becomes:
+```lua
+pty_width = 500,  -- Fixed width prevents truncation
+```
+
+## Technical Details
+
+The issue occurs because:
+1. Overseer's `jobstart` strategy creates a PTY (pseudo-terminal) for running commands
+2. By default, the PTY width matches the current Neovim window width
+3. Many compilers format their output based on terminal width, truncating long lines
+4. This results in incomplete error messages in the quickfix list
+
+The fix allows setting a fixed `pty_width` that's independent of the window size, ensuring full error messages are captured regardless of terminal width.
+
+## Files
+
+- `flake.nix` - Complete self-contained reproducer flake (TEST ONLY - do not commit to main repo)
+
+That's all! The flake contains everything else needed (test C++ code, Neovim config, test script) embedded within it.
+
+**Note:** This `flake.nix` is only for reproducing the issue. It should not be committed to the main overseer.nvim repository. After testing, you can delete it or move it elsewhere.