feat(P3): IHF Phase 3 complete — Governance and Decision Linkage

Implements the full governance layer:
- Schema: requirements, decision_records, policy_references,
  implementation_change_references; requirement_candidates gets
  requirement_id back-reference
- RequirementsController (index/show; promotion-only create)
- DecisionRecordsController (CRUD + policy/impl ref management)
- GovernanceDashboardAction on HubsController (AutoRefresh)
- PromoteToRequirementAction + LinkToDecisionAction on candidates
- Outcome immutability enforced at controller level (fill excludes outcome)
- Full six-outcome vocabulary with Tailwind color roles
- Integration tests for all Phase 3 paths
- FrontController: registers Phase 2 missing controllers + all Phase 3
- SCOPE.md + docs/phase3-summary.md updated

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

Web/View/Requirements/Index.hs

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+module Web.View.Requirements.Index where
+
+import Web.Types
+import Generated.Types
+import IHP.Prelude
+import IHP.ViewPrelude
+
+data IndexView = IndexView
+    { requirements :: ![Requirement]
+    , candidates   :: ![RequirementCandidate]
+    }
+
+instance View IndexView where
+    html IndexView { .. } = [hsx|
+        <div class="flex items-center justify-between mb-6">
+            <h1 class="text-2xl font-semibold">Requirements</h1>
+        </div>
+        {if null requirements
+            then [hsx|<p class="text-sm text-gray-400">No requirements yet. Promote an accepted candidate to create one.</p>|]
+            else renderTable requirements candidates}
+    |]
+
+renderTable :: [Requirement] -> [RequirementCandidate] -> Html
+renderTable reqs candidates = [hsx|
+    <div class="bg-white rounded-lg border border-gray-200 overflow-hidden">
+        <table class="w-full text-sm">
+            <thead class="bg-gray-50 border-b border-gray-200">
+                <tr>
+                    <th class="text-left px-4 py-3 font-medium text-gray-600">Title</th>
+                    <th class="text-left px-4 py-3 font-medium text-gray-600">Status</th>
+                    <th class="text-left px-4 py-3 font-medium text-gray-600">Source Candidate</th>
+                    <th class="text-left px-4 py-3 font-medium text-gray-600">Created</th>
+                </tr>
+            </thead>
+            <tbody class="divide-y divide-gray-100">
+                {forEach reqs (renderRow candidates)}
+            </tbody>
+        </table>
+    </div>
+|]
+
+renderRow :: [RequirementCandidate] -> Requirement -> Html
+renderRow candidates req = [hsx|
+    <tr class="hover:bg-gray-50">
+        <td class="px-4 py-3">
+            <a href={ShowRequirementAction { requirementId = req.id }}
+               class="text-indigo-600 hover:text-indigo-800 font-medium">{req.title}</a>
+        </td>
+        <td class="px-4 py-3">
+            <span class={reqStatusClass req.status <> " text-xs px-2 py-0.5 rounded font-medium"}>
+                {req.status}
+            </span>
+        </td>
+        <td class="px-4 py-3 text-gray-600">
+            {candidateTitle candidates req.sourceCandidateId}
+        </td>
+        <td class="px-4 py-3 text-gray-400 text-xs">{show req.createdAt}</td>
+    </tr>
+|]
+
+candidateTitle :: [RequirementCandidate] -> Id RequirementCandidate -> Text
+candidateTitle cs cid =
+    maybe "(unknown)" (.title) (find (\c -> c.id == cid) cs)
+
+reqStatusClass :: Text -> Text
+reqStatusClass "active"     = "bg-green-100 text-green-800"
+reqStatusClass "superseded" = "bg-yellow-100 text-yellow-800"
+reqStatusClass "withdrawn"  = "bg-gray-100 text-gray-500"
+reqStatusClass _            = "bg-gray-100 text-gray-600"

Web/View/Requirements/Show.hs

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+module Web.View.Requirements.Show where
+
+import Web.Types
+import Generated.Types
+import IHP.Prelude
+import IHP.ViewPrelude
+
+data ShowView = ShowView
+    { requirement :: !Requirement
+    , candidate   :: !RequirementCandidate
+    , widget      :: !Widget
+    , mDecision   :: !(Maybe DecisionRecord)
+    }
+
+instance View ShowView where
+    html ShowView { .. } = [hsx|
+        <div class="mb-6 flex items-center gap-2 text-sm text-gray-500">
+            <a href={RequirementsAction} class="hover:text-gray-700">Requirements</a>
+            <span>/</span>
+            <span>{requirement.title}</span>
+        </div>
+
+        <div class="max-w-3xl space-y-6">
+            <!-- Header card -->
+            <div class="bg-white rounded-lg border border-gray-200 px-6 py-5">
+                <div class="flex items-start justify-between mb-3">
+                    <h1 class="text-2xl font-semibold">{requirement.title}</h1>
+                    <span class={reqStatusClass requirement.status <> " text-xs px-2 py-0.5 rounded font-medium ml-4"}>
+                        {requirement.status}
+                    </span>
+                </div>
+                <p class="text-sm text-gray-700 leading-relaxed">{requirement.description}</p>
+            </div>
+
+            <!-- Source candidate -->
+            <div class="bg-white rounded-lg border border-gray-200 px-6 py-4">
+                <h2 class="text-sm font-semibold text-gray-700 mb-2">Source Candidate</h2>
+                <a href={ShowRequirementCandidateAction { requirementCandidateId = candidate.id }}
+                   class="text-sm text-indigo-600 hover:text-indigo-800">{candidate.title}</a>
+                <p class="text-xs text-gray-400 mt-1">Widget: {widget.name}</p>
+            </div>
+
+            <!-- Linked decision -->
+            <div class="bg-white rounded-lg border border-gray-200 px-6 py-4">
+                <h2 class="text-sm font-semibold text-gray-700 mb-2">Linked Decision</h2>
+                {case mDecision of
+                    Nothing -> [hsx|<p class="text-sm text-gray-400">No decision linked yet.</p>|]
+                    Just dr -> [hsx|
+                        <a href={ShowDecisionRecordAction { decisionRecordId = dr.id }}
+                           class="text-sm text-indigo-600 hover:text-indigo-800">{dr.title}</a>
+                        <span class={outcomeClass dr.outcome <> " text-xs px-2 py-0.5 rounded font-medium ml-2"}>
+                            {dr.outcome}
+                        </span>
+                    |]}
+            </div>
+        </div>
+    |]
+
+reqStatusClass :: Text -> Text
+reqStatusClass "active"     = "bg-green-100 text-green-800"
+reqStatusClass "superseded" = "bg-yellow-100 text-yellow-800"
+reqStatusClass "withdrawn"  = "bg-gray-100 text-gray-500"
+reqStatusClass _            = "bg-gray-100 text-gray-600"
+
+outcomeClass :: Text -> Text
+outcomeClass "accepted"  = "bg-green-100 text-green-800"
+outcomeClass "rejected"  = "bg-red-100 text-red-800"
+outcomeClass "deferred"  = "bg-gray-100 text-gray-600"
+outcomeClass "split"     = "bg-purple-100 text-purple-800"
+outcomeClass "merged"    = "bg-indigo-100 text-indigo-800"
+outcomeClass "reframed"  = "bg-orange-100 text-orange-800"
+outcomeClass _           = "bg-gray-100 text-gray-600"