Improve Story Map readability controls

[hanley-development]

Summary

Improves pjm visualize Story Map readability while keeping the current full graph as the default view.

Changes

• Adds graph metadata for file event counts, failures, directory buckets, and importance.
• Adds Story Map controls:
  • Collapse dense files: replaces files with 10+ attached events with a draggable file bubble.
  • Collapse directories: groups files by directory and supports click-to-drill-down expansion.
  • Expand all: returns to the full graph and clears collapse, expansion, selection, and focus state.
  • Reset focus: clears file focus without changing the active collapse mode.
• Reduces label noise by showing labels for bubbles, selected/focused nodes, high-importance files, fixes, and failed attempts.
• Adds file focus mode that dims unrelated nodes when clicking a file or collapsed file bubble.
• Adds dense-file bubbles for crowded files while preserving mixed multi-file event links.
• Adds directory collapse with drilldown, preserving bridge events between visible directories/files.
• Keeps drag, zoom, and force-graph behavior intact.

Verification

• python -m pytest tests\test_visualize.py -q
• python -m pytest -q
• Generated local visual preview from project .projectmem data.

Dependency

Depends on #6.

Please review and merge #6 first; this PR builds on that branch and should be retargeted to main after #6 lands.