fix(ui): keep latest issue document revision current (#3342)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies.
> - Board users and agents collaborate on issue-scoped documents such as
plans and revisions need to be trustworthy because they are the audit
trail for those artifacts.
> - The issue document UI now supports revision history and restore, so
the UI has to distinguish the current revision from historical revisions
correctly even while multiple queries are refreshing.
> - In `PAPA-72`, the newest content could appear under an older
revision label because the current document snapshot and the
revision-history query could temporarily disagree after an edit.
> - That made the UI treat the newest revision like a historical restore
target, which is the opposite of the intended behavior.
> - This pull request derives one authoritative revision view from both
sources, sorts revisions newest-first, and keeps the freshest revision
marked current.
> - The benefit is that revision history stays stable and trustworthy
immediately after edits instead of briefly presenting the newest content
as an older revision.

## What Changed

- Added a `document-revisions` helper that merges the current document
snapshot with fetched revision history into one normalized revision
state.
- Updated `IssueDocumentsSection` to render from that normalized state
instead of trusting either query in isolation.
- Added focused tests covering the current-revision selection and
ordering behavior.

## Verification

- `pnpm -r typecheck`
- `pnpm build`
- Targeted revision tests passed locally.
- Manual reviewer check:
  - Open an issue document with revision history.
  - Edit and save the document.
  - Immediately open the revision selector.
- Confirm the newest revision remains marked current and older revisions
remain the restore targets.

## Risks

- Low risk. The change is isolated to issue document revision
presentation in the UI.
- Main risk is merging the current snapshot with fetched history
incorrectly for edge cases, which is why the helper has focused unit
coverage.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [ ] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

ui/src/components/IssueDocumentsSection.tsx

@@ -12,6 +12,7 @@ import { useLocation } from "@/lib/router";
 import { ApiError } from "../api/client";
 import { issuesApi } from "../api/issues";
 import { useAutosaveIndicator } from "../hooks/useAutosaveIndicator";
+import { deriveDocumentRevisionState } from "../lib/document-revisions";
 import { queryKeys } from "../lib/queryKeys";
 import { cn, relativeTime } from "../lib/utils";
 import { MarkdownBody } from "./MarkdownBody";
@@ -536,10 +537,10 @@ export function IssueDocumentsSection({
   }, []);
 
   const previewRevision = useCallback((doc: IssueDocument, revisionId: string) => {
-    const revisions = getDocumentRevisions(doc.key);
-    const selectedRevision = revisions.find((revision) => revision.id === revisionId);
+    const revisionState = deriveDocumentRevisionState(doc, getDocumentRevisions(doc.key));
+    const selectedRevision = revisionState.revisions.find((revision) => revision.id === revisionId);
     if (!selectedRevision) return;
-    if (selectedRevision.id === doc.latestRevisionId) {
+    if (selectedRevision.id === revisionState.currentRevision.id) {
       returnToLatestRevision(doc.key);
       return;
     }
@@ -787,7 +788,10 @@ export function IssueDocumentsSection({
           const activeDraft = draft?.key === doc.key && !draft.isNew ? draft : null;
           const activeConflict = documentConflict?.key === doc.key ? documentConflict : null;
           const isFolded = foldedDocumentKeys.includes(doc.key);
-          const revisionHistory = getDocumentRevisions(doc.key);
+          const rawRevisionHistory = getDocumentRevisions(doc.key);
+          const revisionState = deriveDocumentRevisionState(doc, rawRevisionHistory);
+          const revisionHistory = revisionState.revisions;
+          const currentRevision = revisionState.currentRevision;
           const selectedRevisionId = selectedRevisionIds[doc.key] ?? null;
           const selectedHistoricalRevision = selectedRevisionId
             ? revisionHistory.find((revision) => revision.id === selectedRevisionId) ?? null
@@ -795,10 +799,10 @@ export function IssueDocumentsSection({
           const isHistoricalPreview = Boolean(selectedHistoricalRevision);
           const displayedTitle = selectedHistoricalRevision
             ? selectedHistoricalRevision.title ?? ""
-            : activeDraft?.title ?? doc.title ?? "";
-          const displayedBody = selectedHistoricalRevision?.body ?? activeDraft?.body ?? doc.body;
-          const displayedRevisionNumber = selectedHistoricalRevision?.revisionNumber ?? doc.latestRevisionNumber;
-          const displayedUpdatedAt = selectedHistoricalRevision?.createdAt ?? doc.updatedAt;
+            : activeDraft?.title ?? currentRevision.title ?? "";
+          const displayedBody = selectedHistoricalRevision?.body ?? activeDraft?.body ?? currentRevision.body;
+          const displayedRevisionNumber = selectedHistoricalRevision?.revisionNumber ?? currentRevision.revisionNumber;
+          const displayedUpdatedAt = selectedHistoricalRevision?.createdAt ?? currentRevision.createdAt;
           const showTitle = !isPlanKey(doc.key) && !!displayedTitle.trim() && !titlesMatchKey(displayedTitle, doc.key);
           const canVoteOnDocument = Boolean(doc.latestRevisionId && doc.updatedByAgentId && !doc.updatedByUserId && onVote);
 
@@ -845,12 +849,12 @@ export function IssueDocumentsSection({
                       </DropdownMenuTrigger>
                       <DropdownMenuContent align="start" className="w-72">
                         <DropdownMenuLabel>Revision history</DropdownMenuLabel>
-                        {revisionMenuOpenKey === doc.key && isFetchingDocumentRevisions && revisionHistory.length === 0 ? (
+                        {revisionMenuOpenKey === doc.key && isFetchingDocumentRevisions && rawRevisionHistory.length === 0 ? (
                           <DropdownMenuItem disabled>Loading revisions...</DropdownMenuItem>
                         ) : revisionHistory.length > 0 ? (
-                          <DropdownMenuRadioGroup value={selectedRevisionId ?? doc.latestRevisionId ?? ""}>
+                          <DropdownMenuRadioGroup value={selectedRevisionId ?? currentRevision.id ?? ""}>
                             {revisionHistory.map((revision) => {
-                              const isCurrentRevision = revision.id === doc.latestRevisionId;
+                              const isCurrentRevision = revision.id === currentRevision.id;
                               return (
                                 <DropdownMenuRadioItem
                                   key={revision.id}