PAP-10430: split Issue-to-Task copy migration (#7651)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work.
> - The board UI is the operator surface where users create, assign,
monitor, and review work items.
> - The product language is moving toward "tasks" for user-facing work
items while the internal API and database still use "issues".
> - PR #7543 bundled this copy migration with broader
information-architecture work, which made the branch too large for
Greptile review.
> - This pull request peels the Issue-to-Task copy migration into a
smaller, independently reviewable change.
> - The benefit is clearer user-facing terminology, less agent confusion
via the Paperclip skill note, and a smaller PR that Greptile can review.

## Linked Issues or Issue Description

Refs #7645
Refs #7543
Refs PAP-10430

This PR was split out of #7543 so the Issue-to-Task copy migration can
be reviewed separately and the remaining IA PR can fall under Greptile's
file limit.

## What Changed

- Preserves Scott Tong's original `PAP-57` copy-only commit, with author
and co-author credit intact, to rename user-facing "Issues" copy to
"Tasks" across the UI while keeping routes/API/internal symbols as
`issue`.
- Updates onboarding and release-smoke browser selectors from `Create &
Open Issue` to `Create & Open Task`.
- Adds a terminology note to `skills/paperclip/SKILL.md` clarifying that
task and issue refer to the same Paperclip work item.
- Resolves the only cherry-pick conflict by keeping current search
artifacts support and changing visible search copy to "tasks".

## Verification

- `pnpm --filter @paperclipai/ui build` passed.
- `NODE_ENV=test pnpm exec vitest run
ui/src/components/IssuesList.test.tsx ui/src/components/Sidebar.test.tsx
ui/src/components/NewIssueDialog.test.tsx
ui/src/pages/IssueDetail.test.tsx` passed: 4 files, 66 tests.
- `git diff --check origin/master...HEAD` passed.
- Diff is 80 files, below Greptile's 100-file limit.
- Before/after UI copy examples: "Issues" -> "Tasks", "New Issue" ->
"New Task", "Create & Open Issue" -> "Create & Open Task".

## Risks

- Medium copy-risk: this intentionally changes user-facing terminology
broadly while keeping internal issue identifiers and routes unchanged.
- Some docs and APIs still say `issue`; the skill note clarifies this so
agents do not treat task and issue as separate entities.
- Browser-level visual validation is expected from CI because this local
container is missing usable browser dependencies.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

Scott Tong authored the original `PAP-57` copy migration, assisted by
Claude Opus 4.8 and Paperclip agents per the preserved commit metadata.
Codex / GPT-5-class coding agent with shell, GitHub CLI, and repository
access performed the PR split, conflict resolution, skill note, and
verification.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] 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] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: scotttong <scott.tong@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Paperclip <noreply@paperclip.ing>

ui/src/components/IssueRunLedger.tsx

@@ -75,7 +75,7 @@ const LIVENESS_COPY: Record<RunLivenessState, LivenessCopy> = {
   completed: {
     label: "Completed",
     tone: "border-emerald-500/30 bg-emerald-500/10 text-emerald-700 dark:text-emerald-300",
-    description: "Issue reached a terminal state.",
+    description: "Task reached a terminal state.",
   },
   advanced: {
     label: "Advanced",
@@ -95,7 +95,7 @@ const LIVENESS_COPY: Record<RunLivenessState, LivenessCopy> = {
   blocked: {
     label: "Blocked",
     tone: "border-yellow-500/30 bg-yellow-500/10 text-yellow-700 dark:text-yellow-300",
-    description: "Run or issue declared a blocker.",
+    description: "Run or task declared a blocker.",
   },
   failed: {
     label: "Failed",
@@ -535,7 +535,7 @@ export function IssueRunLedgerContent({
   }, [activityEvents, canRenderActivityEvents, ledgerRuns]);
 
   return (
-    <section className="space-y-3" aria-label="Issue run ledger">
+    <section className="space-y-3" aria-label="Task run ledger">
       <div className="flex items-center justify-between gap-2">
         <div className="min-w-0">
           <h3 className="text-sm font-medium text-muted-foreground">Run ledger</h3>
@@ -678,8 +678,8 @@ export function IssueRunLedgerContent({
       {feedItems.length === 0 ? (
         <div className="rounded-md border border-dashed border-border px-3 py-3 text-sm text-muted-foreground">
           {renderActivityEvent
-            ? "Runs and activity will appear here once this issue has history."
-            : "Historical runs without liveness metadata will appear here once linked to this issue."}
+            ? "Runs and activity will appear here once this task has history."
+            : "Historical runs without liveness metadata will appear here once linked to this task."}
         </div>
       ) : (
         <div className="space-y-1.5">