Show real work progress in tree

[chudodey]

What changed

• added honest tree activity metadata that excludes the original capture block from evidence of work
• added accessible node states for untouched, worked, recently active, and done
• showed session count, accumulated minutes, work notes, and last-touch date on nodes
• added absolute branch progress as touched / done / total without percentages
• added a visible text-and-color legend
• added serializer coverage and a seventh real-browser E2E flow
• marked TREE-001 complete and moved the backlog starting point to MOOD-001

Why

The tree previously rendered untouched tasks and repeatedly worked tasks almost identically. That hid the user's effort and made it impossible to see which branches were moving without opening every card.

Validation

• pytest -q — 132 passed, 1 skipped
• python scripts/run_e2e.py — 7 passed
• ruff check src tests e2e scripts main.py
• node --check web/static/app.js
• python scripts/backlog.py --check