F-44: Threading-model task table drift #47

Severity: LOW · Effort: Small · Batch: 5 · Status: Done in #21 (29b54d2), documentation only; the measured column waits on #36 (F-33)

Found in the second full review of the firmware. Recorded with the rest of the pass (F-19…F-44) in docs/REVIEW_REMEDIATION_PLAN_2.md, which is where its status is kept.

THREADING_MODEL.md's table is missing wifi_scan (4 KB), and will need the measured figures
from F-33. (It was also missing jmri_connect; batch 3 removed that task, folding it into
jmri_conn, which the table now lists.)

Acceptance Criteria

• The table lists wifi_scan, settings_writer and stack_report, both WebSocket tasks
  with their sizes, and the IDF tasks our callbacks run on. jmri_save is gone, and the
  LVGL task carries its real name, lvgl.
• The measured column is filled in (F-33).