docs: mark completion and the answer split done, record tips

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TqXevQJhxFrM7jJg82cgZN

docs/TODO.md

@@ -318,13 +318,14 @@ Analysis**, which has three tabs.
 - [ ] **Performance over time** — a line of the headline score by date, with an
       honest empty state ("complete more questions to unlock this chart")
       rather than a chart drawn through two points.
-- [ ] **Analysis panel beside it**, with **All attempts / Latest attempt**
-      tabs: a donut split correct / correct-with-hints / incorrect, a sentence
-      naming attempts and unique questions, and the three figures written out
-      beneath. This is the pattern to copy for our own session analysis.
-- [ ] **Completion** — four figures (questions answered n/total, answered
-      correctly, time per question, total time spent) with an **Edit time
-      range** control, so "this month" and "all time" are different questions.
+- [x] **Analysis panel beside it** — done 2026-09-12. `GET
+      /study-tools/answer-split` counts the same answers twice: every answer
+      ever given, and the most recent answer to each question. The donut is
+      shared with the session view (`components/Donut`) and splits correct /
+      correct after a tip / incorrect / unanswered.
+- [x] **Completion** — done 2026-09-12. `GET /study-tools/completion?days=N`
+      over 7 / 30 / 90 days or all time. Repetitions, course quizzes and
+      expired attempts are left out; a blank is not a wrong answer.
 
 ### Recommendations
 
@@ -508,7 +509,9 @@ category management page · tag vocabulary sanitised · question manager with bu
 editing · per-category educator grants · full-page question editor · session
 rail with gradual reveal · articles read as one page · practise-this-topic ·
 continue-study panel · PREP study plans · question version history ·
-exam-scoped disciplines.
+exam-scoped disciplines · tips in the prose (`{{phrase|tip}}`, underlined,
+opening where the phrase is) and the hint slice on the donut that goes with
+them.
 
 ## From the 11 Sep recordings — still open
 - **Quiz player, "let it not be showing when you're taking the quiz"** — the recording does not say what "it" is. Most likely reading: in exam mode the right-hand question rail must not reveal right/wrong as you go (study mode may). Confirm before changing.