Merge origin/main (v1.91.9.0, #2998) into capy/audit-fix-wave; release as v1.91.10.0

Main shipped v1.91.9.0, so this wave becomes v1.91.10.0. Conflicts kept this
branch's planner-derived assertions. Main's new test-value eval gets rule
kinds for its three gate cases and its measured 332 s duration from #2998's
CI; census counts and the PR fallback floor follow the new file. The packing
test now weighs each tier's recorded durations the way the planner does.

gstack/llms.txt

@@ -65,6 +65,7 @@ Conventions:
 - [/skillify](skillify/SKILL.md): Codify the most recent successful /scrape flow into a permanent browser-skill on disk.
 - [/spec](spec/SKILL.md): Turn vague intent into a precise, executable spec in five phases.
 - [/sync-gbrain](sync-gbrain/SKILL.md): Keep gbrain current with this repo's code and refresh agent search guidance in CLAUDE.md.
+- [/test-audit](test-audit/SKILL.md): Find low-value or duplicate tests and the test-only code they keep alive.
 - [/unfreeze](unfreeze/SKILL.md): Clear the freeze boundary set by /freeze, allowing edits to all directories again.
 
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