Bug: concore stop can kill unrelated processes (false positive pattern matching) #623

Description

concore stop uses broad substring matching to identify processes to kill. This matches any process whose command line contains the word concore - including editors, git operations, IDEs, and other tools that happen to have concore files open.

Steps to Reproduce

1. Open a concore file in VS Code: code concore/README.md
2. Run concore stop
3. VS Code gets killed because its cmdline contains concore

Other false positives:

• git -C concore pull
• grep -r concore ./src
• vim concore/concore_base.py
• notepad.exe C:\repos\concore\concore.py

Expected Behavior

concore stop should only kill actual concore study processes, not editors, git, or other tools that happen to reference concore files.

Affected Files

• concore_cli/commands/stop.py (L24-L32)
• concore_cli/commands/status.py (same detection logic)

Proposed Fix

Replace the broad substring check with strict multi-tier detection:

1. PID registry - trust concorekill_pids.txt written at study startup
2. concorekill.bat - only spawned by concore itself
3. Regex matching - only match actual concore executions
4. CLI token matching - match concore stop, concore build, etc.
5. cwd marker files - check for concore.iport + concore.py in working directory

Status

PR already opened: #622