fix(rendering): slice 19 — collapsed-running null-paint (corpus new-bug count → 0) - #451

…new-bug)

The dangling-tool-chip defect (corpus 2026-06-29 1b2b5e96): collectTurn
selected every finalized tool block regardless of result arrival, so a
history turn whose churn-tool run never resolved painted a permanently
dangling chip legacy deliberately withheld.

Rule (policy bit hideUnresolvedHistoryTools, CLAUDE ONLY per D10):
reject a semantic-HISTORY tool-use candidate with reason
'collapsed-running' when ALL hold: toolName in the legacy
collapsed_activity churn set (Read/FileRead/Glob/Grep/Bash), no
block-local result evidence (resultContent/resultAt/resultIsError),
and no committed tool_use/tool_result trace. Current-turn tools always
paint (streaming legitimately awaits results); codex exempt (MCP
delivers function_call_output in a LATER turn - the corpus proved the
broader rule over-fires there within one run: 15 fixtures); non-churn
tools (Task, AskUserQuestion, MCP) paint even unresolved - a running
Task chip is live subagent signal.

Corpus archaeology bonus: three fixtures gained missing-in-next turns
that looked like over-suppression but are outdated oracles - legacy's
OWN paintsDom gate landed 2026-06-24 (1254bed), and those bundles were
captured before it. All five structurally-identical turns carry
lookups.toolCallsById status in_progress; modern legacy hides them
exactly like this rule does. Verdicted with the commit citation.

Corpus final state: 0 untriaged, 0 new-bug across all 46 fixtures.
137 pipeline tests.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>