fix(ui): remove New Task heading from composer (#18604)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work.
> - People use the task composer to describe work for an agent.
> - The Coordinator workspace added a visible New Task heading above the
editor.
> - This heading adds text and space that the task form does not need.
> - This pull request removes the heading and its empty header space.
> - The composer keeps its task fields and creation controls.

## Linked Issues or Issue Description

**What happened?**

The task composer shows a New Task heading when Coordinator is on.
Commit 71f0c0c99e added this text in
#17983 on October 28, 2026.

**Expected behavior**

The task composer opens without the extra visible heading or blank
header space.

**Steps to reproduce**

1. Enable Coordinator in Settings > Experimental.
2. Open the new task composer.
3. Look above the description editor.

**Paperclip version or commit**

Verified from source based on 06bc8db75.

**Deployment mode**

Source checkout. This is a UI change.

Related work: #17983 introduced the heading. A search found no open PR
that removes it.

## What Changed

- Remove the Coordinator-only New Task paragraph from `NewIssueDialog`.
- Remove Coordinator from the header condition to prevent empty header
space.
- Update the existing creation test to check that the heading is absent
with Coordinator on and off.

## Verification

- `pnpm exec vitest run ui/src/components/NewIssueDialog.test.tsx`: 111
tests passed. This includes description-only creation with Coordinator
on and off, saved titles, sub-tasks, and pending creation states.
- `pnpm check:token-gates`: passed.
- `pnpm --filter @paperclipai/ui typecheck`: passed.
- `pnpm --filter @paperclipai/ui build`: passed when run separately.
- Full workspace typecheck and build could not complete because the
sandbox has no `cargo` command. Runner TypeScript checks completed
before this limit.
- The first UI build was killed with exit 137 while the full test suite
ran. The 8 GiB sandbox reports one OOM kill. The full local suite was
stopped without a verdict to free memory. The separate UI build then
passed. CI runs the required checks on this commit.
- Greptile reviewed commit `82d90c97e018f1677fcbf85b9e0713a4eebe4115`:
5/5, no review comments.
- Browser and release suites were not run. This change removes one
paragraph and its header condition. Existing component tests cover the
changed states.

## Risks

- Low risk. The header still shows saved titles, parent task context,
pending sends, and retry errors under their existing conditions.
- No API, database, permission, or design token changes.
- No documentation changes are needed for this text removal.

## Model Used

- OpenAI Codex, GPT-6 family, with reasoning, tool use, and code
execution. The runtime does not expose the exact model ID or context
window size.

## 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 not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] 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: Paperclip <noreply@paperclip.ing>

ui/src/components/NewIssueDialog.tsx

@@ -1515,7 +1515,7 @@ function AccountNewIssueDialog({ ignoreDefaults }: { ignoreDefaults: boolean })
                 runSettings: composerSettings,
                 onRunSettingsChange: setComposerSettings,
                 header:
-                  hasTitle || isSubIssueMode || coordinatorEnabled || durableCreate.pending || resendError ? (
+                  hasTitle || isSubIssueMode || durableCreate.pending || resendError ? (
                     <div className="mb-3 flex flex-col gap-2 text-xs">
                       {durableCreate.pending && durableCreate.status !== "sending" ? (
                         <PendingSendNotice
@@ -1575,7 +1575,6 @@ function AccountNewIssueDialog({ ignoreDefaults }: { ignoreDefaults: boolean })
                           </div>
                         </div>
                       ) : null}
-                      {coordinatorEnabled ? <p className="text-sm font-medium text-foreground">New Task</p> : null}
                     </div>
                   ) : undefined,
                 details: (