fix(config): set proactive is case-insensitive; follow-up #3446 cited; test hygiene

set proactive OFF warned and stored core, the opposite of the opt-out typed; the value is lowercased first, as gstack-skill-start does for a hand edit. The fixture git init carries the tripwire timeout, the source-shape assertion on the private _PROACTIVE_OFF line goes (the routing-offer test proves the behavior), and the CHANGELOG Tests bullets collapse to one per file with the known gap pointing at #3446. Found by /ship's full repeat pass and its tests lane.

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

docs/proactive.md

@@ -39,7 +39,7 @@ already in CLAUDE.md stays; delete it yourself). Under `core` the offered
 section still lists every routing rule and tells the host to invoke any
 matching skill. If you accepted it before the `core` default, trim that section
 to the four core rules (or delete it and let gstack offer it again); making the
-offered section follow `core` is tracked as a follow-up.
+offered section follow `core` is tracked in #3446.
 
 gstack asks once, after the telemetry question, which of the three you want.
 "Say stop suggesting" in a session runs `gstack-config set proactive off` for you.