feat(quest): QT6 — plugins can read the contract tracker

The last piece of QT6's own scope: r10-quest-dialogs.md §11.6's contract half.
IGameState.Contracts exposes what the client structurally knows about quests,
which — per that same research — is the tracker and nothing else. The rest of
§11.6 (chat stream, tells, give, use, confirmations) is other features and
stays out of this campaign.

A pull-through source rather than a pushed mirror. Contracts change rarely and
are already owned canonically, so a second copy would only be a thing to keep
in step; reading through means a plugin cannot observe a stale list.

Both hosts implement it. The headless one carries contract id, stage and
progress but no names — a bot has no dat access — because losing the TEXT is
expected while losing the QUEST would leave a bot silently unable to see what
it is on. Same rule covers a contract the installed dat has never heard of: it
still projects, with empty text and a correct status, rather than vanishing.

The interface member is defaulted so a host predating this campaign still
satisfies IGameState.

Two lazy catalog loads exist (the panel's and this one) rather than one shared
instance. That is deliberate: threading a shared ContractCatalog through three
composition records to avoid reading a 322-row immutable table at most twice
per session would be plumbing for no correctness or performance gain, and the
comment at the call site says so.

Campaign QT is complete; the connected user gate is owed.

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

docs/plans/2026-08-21-contract-tracker-campaign.md

@@ -174,6 +174,13 @@ the toolbar was ported — it simply had no panel registered behind it, so
 clicking it did nothing. Registering slot 25 completed a wiring that was
 already three-quarters present.
 
+**The plugin surface** (`r10-quest-dialogs.md` §11.6's contract half) ships as
+`IGameState.Contracts`, projected through `ContractPluginProjection` — a
+pull-through view of the canonical tracker, never a mirror. Both hosts
+implement it; the headless one carries the numeric fields without the authored
+text, since a bot has no dat access. The rest of §11.6 (chat stream, tells,
+give, use, confirmations) is other features and stays out of Campaign QT.
+
 ### Owed
 
 - The connected user gate: accept a quest against live ACE, open the Journal