Fix PATH accumulation when switching between projects with .luca/tools

[albertodebortoli]

Problem

When navigating between two directories that both contain a .luca/tools folder, the PATH would accumulate entries for both projects. More critically, switching back to the first project would leave the second project's entry at a higher priority position in PATH, causing the wrong tool version to be resolved.

Reproduction steps:

1. cd /path/to/project-A — project-A/.luca/tools is added to PATH
2. cd /path/to/project-B — project-B/.luca/tools is added to PATH (now both are present)
3. cd /path/to/project-A — project-A/.luca/tools is already in PATH, so the function returns early. project-B/.luca/tools remains and is still first in PATH.

The result is that tools from project B are resolved instead of project A's tools.

Root Cause

In update_path(), the cleanup loop that removes stale .luca/tools entries was placed inside an else branch — it only ran when the current directory had no .luca/tools folder:

if [ -d "$tool_bin_dir" ]; then
    # add to PATH...
else
    # ← cleanup only ran here, never when both dirs have .luca/tools
    if [[ ":$PATH:" == *"/$TOOL_FOLDER/tools:"* ]]; then
        # strip stale entries...
    fi
fi

When navigating from project A to project B (both having .luca/tools), the if branch fires, skips cleanup entirely, and simply appends B's entry. The stale A entry is never removed until you navigate to a directory with no .luca/tools at all.

Fix

Move the cleanup loop unconditionally to the top of update_path(), before the add step. The function now always:

1. Scans PATH for any */.luca/tools entries
2. Keeps only those whose project root is an ancestor of (or equal to) $PWD
3. Appends the current directory's tool_bin_dir if it exists and isn't already present

update_path() {
  local tool_bin_dir="$(pwd)/$TOOL_FOLDER/tools"
  local current_pwd="$(pwd)"

  # Always clean up stale entries first
  if [[ ":$PATH:" == *"/$TOOL_FOLDER/tools:"* ]]; then
    # ... strip any entry whose project root doesn't match $PWD ...
    export PATH="$new_path"
  fi

  # Then add current entry if needed
  if [ -d "$tool_bin_dir" ]; then
    case ":$PATH:" in
      *":$tool_bin_dir:"*) ;;
      *) export PATH="$tool_bin_dir:$PATH" ;;
    esac
  fi
}

Behaviour After Fix

Navigation	PATH result
cd project-A	project-A/.luca/tools:...
cd project-B	project-B/.luca/tools:... (A's entry removed)
cd project-A	project-A/.luca/tools:... (B's entry removed)
cd /no-luca-dir	... (all .luca/tools entries removed)
cd project-A/subdir	project-A/.luca/tools:... (parent project entry preserved)

All existing idempotency and subdirectory-traversal behaviour is preserved.