Fix weapon set branch path allocation

[unrealdreamz]

Summary

Prevent normal passive allocation from continuing through weapon-set-only branches.

Fixes #1532

Root Cause

Passive path construction treats every allocated node as a path root without remembering which root produced a candidate path. That means a node at the end of a weapon-set branch can become the closest root for the next unallocated passive. When allocation mode is switched back to normal, AllocNode only checks that a path exists, so it can allocate a normal passive from a weapon-set-only branch.

Fix

• Track the allocated root that produced each passive path via pathRoot.
• Clear pathRoot whenever paths are rebuilt, alongside path/pathDist.
• In normal allocation mode, reject paths rooted in an allocated weapon-set node or explicitly passing through one.
• Leave weapon-set mode allocation unchanged.
• Added a focused passive-spec regression that:
  • allocates one normal node,
  • allocates the next node in weapon set 1,
  • proves normal mode cannot continue beyond that branch,
  • proves weapon set 1 still can.

Validation

Local validation run:

git diff --check
PASS (CRLF normalization warnings only)

git diff --cached --check
PASS (CRLF normalization warnings only)

git show --check --stat --oneline HEAD
PASS (CRLF normalization warnings only)

I did not run Docker/Busted locally because the available full test runner is container-based and I was avoiding external test containers/windows during this session.

Risk / Rollback

Risk is localized to passive allocation/path bookkeeping. The guard applies only while normal allocation mode is selected; weapon-set mode continues to use the existing path behavior. Rollback is the single commit if an unexpected valid normal-path edge case appears.