docs: record 0.8.5 acceptance and the 0.9 referral mechanism

Ticks Slice 0.8.5's acceptance criteria against the implemented
behavior, verified against the seed and service code rather than
assumed, and notes that the Bandit Blade's World Renown 3 gate is
deliberately unreachable until Slice 0.11 adds the milestones to
reach it.

Points Slice 0.9 at the concrete bypass mechanism that now exists
(BORIN_OFFER_IDS.hideBag's bypassConditions flag) instead of the
placeholder reference to "the quest/referral exception".

Also commits the slice's plan and research-notes documents, which
were untracked.

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

docs/playable-slices/0.9-First-Quest-and-Bag-Tutorial.md

@@ -133,7 +133,16 @@ Category: HIDE
 Capacity: 5
 ```
 
-The grant should use the quest/referral exception supported by Slice 0.8.5.
+The grant uses the referral exception built in Slice 0.8.5: the Basic Hide Bag
+offer (`BORIN_OFFER_IDS.hideBag`) carries
+
+```text
+bypassConditions: [{ type: FLAG_SET, key: 'referred-by-south-gate-warden' }]
+```
+
+so setting that flag on the character's Borin state opens the offer without
+changing any reputation. The offer's own gate stays at Border Watch
+Reputation 40.
 
 ---