fix(WP-0014/A2): close remaining pure-param and structural compilation errors

Convert all remaining `<- paramOrNothing / param / paramOrDefault /
currentUserOrNothing` monadic binds to `let` — these functions are pure
(ImplicitParams-based) in IHP v1.5, so `<-` is a type error in an IO
do-block.

Controllers fixed:
  AgentDelegations, AiGovernancePolicies, Annotations, ApiConsumers,
  CollectiveProposals, DecisionRecords, DeploymentRecords,
  HubCapabilityManifests, HubRoutingRules, InstitutionalKnowledge,
  OutcomeCorrelations, RequirementCandidates, TypeRegistries,
  WebhookSubscriptions, Widgets,
  Api/V2/{Annotations,InteractionEvents,Token}

WebhookSubscriptions: remove orphaned `Right () ->` case arm that was
left inside a bare `unless` block (structural parse error).

Also carries forward all in-progress fixes from the working tree:
  helpers (AgentBridge, ApiRateLimit, BottleneckDetector,
            CrossHubPropagation, FrictionScore),
  views (CanSelect instances, HSX lambda extraction, formFor wrappers),
  env/build (envrc GHCi perms, flake.nix Tailwind + GHC resource limits,
             static/app.css additional Tailwind output).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Web/Controller/Api/V2/Learning.hs

@@ -14,8 +14,8 @@ instance Controller ApiV2LearningController where
 
     action ApiV2IndexOutcomeCorrelationsAction = do
         _consumer <- requireApiConsumer
-        mHubId    <- paramOrNothing @(Id Hub) "hub_id"
-        mCat      <- paramOrNothing @Text "category"
+        let mHubId    = paramOrNothing @(Id Hub) "hub_id"
+            mCat      = paramOrNothing @Text "category"
         (page, perPage) <- getPageParams
         let off = (page - 1) * perPage
         baseQuery <- pure $ query @OutcomeCorrelation
@@ -43,7 +43,7 @@ instance Controller ApiV2LearningController where
 
     action ApiV2IndexKnowledgeBaseAction = do
         _consumer <- requireApiConsumer
-        mQ        <- paramOrNothing @Text "q"
+        let mQ        = paramOrNothing @Text "q"
         (page, perPage) <- getPageParams
         let off = (page - 1) * perPage
         rows <- case mQ of