practice: the between-problems pause — conclude ends the turn, the learner's go-ahead paces the stream (round 16)

Owner ruling (2026-10-06): every concluded problem opens a pause. The
agent may speak its closing words about the learner's last thinking
after the conclude result, then ENDS ITS TURN — a system-prompt law
deliberately, per owner correction, NOT tool-level terminate. The next
problem is never posed until the learner explicitly moves on; the pause
is the session's teaching space (repairs, clarifications, follow-ups —
still surgical, never re-teaching).

The move-on signal is a first-class input: { type: "next" } appends a
practice-next marker (content = single-sourced NEXT_PROBLEM_TEXT — the
model's unambiguous go-ahead: pose per the selection rules or wrap if
the arc is complete). Honest 400s: practice sessions only, nothing
active (mid-problem input rides the dock), riding after any pending
dismissal synthesis exactly like text.

The fast path (owner approved: composer-band chip + Enter-on-empty):
- Composer.enterAction gains "next" — Enter on an EMPTY composer in
  the pause fires the signal; typing anything makes Enter a send again;
  busy (steer/stop) outranks the pause.
- The Next chip hovers at the composer band's top-right (pick-pill
  chrome register) whenever the pause is live and a problem has ever
  been posed; the placeholder becomes the hint ("Ask about this
  problem — or press Enter for the next one…", exact);
- the transcript renders the signal as a compact centered NEXT PROBLEM
  line (mono-caps chrome); session-core appends it optimistically.

CONCLUDE_ACK_TEXT rewritten to carry the law; doctrine §VIII gains the
pause law (owner-sanctioned edit #3); 00-base's conclude/dismissal
bullets rewritten + the between-problems section added.

src/agent/prompts/practice/10-doctrine.md

@@ -1,7 +1,8 @@
-<!-- Copied from the owner's doctrine (2026-10-04 20.37) with one approved edit:
-     §I material-arrival generalized (verbal descriptions, outside problems).
-     Tool mechanics live in 00-base.md; theory in
-     docs/vision-practice-sessions.md's source note. -->
+<!-- Copied from the owner's doctrine (2026-10-04 20.37) with approved edits:
+     §I material-arrival generalized (verbal descriptions, outside problems);
+     §VIII pause law (owner round 16, 2026-10-06: concluding ends the turn;
+     the learner's explicit go-ahead paces the stream). Tool mechanics live
+     in 00-base.md; theory in docs/vision-practice-sessions.md's source note. -->
 
 # The practice session
 
@@ -116,7 +117,7 @@ Classify every miss: cue miss (nothing came), discrimination error (wrong candid
 
 ## VIII. Progression
 
-A claimed answer is not a signal to progress. You own progression, not the answer count. A problem may take many claims; staying is the default while yield remains.
+A claimed answer is not a signal to progress. You own progression, not the answer count. A problem may take many claims; staying is the default while yield remains. Concluding ends your turn; the next problem is posed only when the learner explicitly moves on — the pause between problems is theirs to use (questions, repairs, clarifications) and theirs to end.
 
 Move on when the problem is solved correctly; when the learner surrenders or cannot proceed; or when the marginal yield of staying is exhausted — flailing, repeated misses, frustration. Moving on spends a reveal: the committed solution becomes visible to the learner when the next problem is assigned. Do not spend reveals for nothing, and do not withhold them past the point of exhaustion.