Guard assigned backlog liveness (#5428)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - The issue graph and liveness recovery system decide whether assigned
work is executable or parked
> - Assigned issues created without an explicit status could silently
land in backlog, making parents look blocked with no productive wake
path
> - The server, shared validators, recovery analysis, and UI all need to
agree on that execution semantic
> - This pull request makes assigned issue creation default to `todo`,
flags assigned backlog blockers, and surfaces the state in the board
> - The benefit is that parked assigned work becomes intentional and
visible instead of creating silent liveness stalls

## What Changed

- Adds contract tests for assigned issue creation defaults.
- Defaults assigned issue creation to `todo` when status is omitted
while preserving explicit `backlog` parking.
- Exposes `resolveCreateIssueStatusDefault` through shared validators.
- Teaches liveness/blocker attention paths to distinguish assigned
backlog blockers.
- Adds UI notices, row/header badges, and issue detail safeguards for
assigned backlog blockers.
- Adds Storybook fixtures and execution-semantics documentation for the
assigned-backlog behavior.

## Verification

- `pnpm run preflight:workspace-links && pnpm exec vitest run
packages/shared/src/validators/issue.test.ts
server/src/__tests__/issue-assigned-backlog-contract-routes.test.ts
server/src/__tests__/issue-blocker-attention.test.ts
server/src/__tests__/issue-liveness.test.ts
server/src/__tests__/heartbeat-issue-liveness-escalation.test.ts
ui/src/components/IssueAssignedBacklogNotice.test.tsx
ui/src/components/IssueRow.test.tsx` — 50 passed, 23 skipped.
- Skipped tests were embedded Postgres suites on this host with the repo
skip message: `Postgres init script exited with code null. Please check
the logs for extra info. The data directory might already exist.`
- Pairwise merge check against the issue-controls PR branch completed
without conflicts via `git merge --no-commit --no-ff` in a temporary
worktree.
- Screenshots for assigned-backlog UI states:
[light](docs/pr-screenshots/pr-5428/assigned-backlog-light.png),
[dark](docs/pr-screenshots/pr-5428/assigned-backlog-dark.png).
- Follow-up checks: `pnpm --filter /ui typecheck`; `pnpm --filter
/mcp-server build`; `pnpm --filter /mcp-server test`; `pnpm exec vitest
run packages/shared/src/validators/issue.test.ts`; focused UI component
tests.
- Remote PR checks on head `6300b3c`: policy, verify, serialized server
shards 1/4-4/4, Canary Dry Run, e2e, Greptile Review, and Snyk all
passed.

## Risks

- Medium: changes status defaulting for assigned issue creation when the
caller omits status. Explicit `backlog` remains supported, and
server/shared tests cover both paths.
- Medium: liveness classification changes can affect blocker attention
labels; focused service and UI tests cover the new assigned-backlog
state.

> 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

- OpenAI Codex coding agent, GPT-5 model family (`gpt-5`), tool-enabled
Paperclip heartbeat environment. Context window and internal reasoning
mode are not exposed by the runtime.

## 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 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] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

server/src/routes/issues.ts

@@ -17,6 +17,7 @@ import {
   checkoutIssueSchema,
   createChildIssueSchema,
   createIssueSchema,
+  resolveCreateIssueStatusDefault,
   feedbackTargetTypeSchema,
   feedbackTraceStatusSchema,
   feedbackVoteValueSchema,
@@ -137,6 +138,44 @@ type SuccessfulRunHandoffActivityRow = {
   createdAt: Date;
 };
 
+function applyCreateIssueStatusDefault(req: Request, res: Response, next: () => void) {
+  if (!req.body || typeof req.body !== "object" || Array.isArray(req.body)) {
+    next();
+    return;
+  }
+
+  const resolution = resolveCreateIssueStatusDefault(req.body as Record<string, unknown>);
+  res.locals.createIssueStatusDefault = resolution;
+  if (resolution.defaulted) {
+    req.body = {
+      ...req.body,
+      status: resolution.status,
+    };
+  }
+  next();
+}
+
+function buildCreateIssueActivityStatusDetails(
+  issue: { assigneeAgentId: string | null; status: string },
+  res: Response,
+) {
+  const statusDefault = res.locals.createIssueStatusDefault as
+    | ReturnType<typeof resolveCreateIssueStatusDefault>
+    | undefined;
+  const assignmentWakeSkipped = !issue.assigneeAgentId || issue.status === "backlog";
+  return {
+    status: issue.status,
+    statusDefaulted: statusDefault?.defaulted ?? false,
+    statusDefaultReason: statusDefault?.reason ?? "explicit",
+    assignmentWakeSkipped,
+    assignmentWakeSkipReason: assignmentWakeSkipped
+      ? issue.assigneeAgentId
+        ? "assigned_backlog"
+        : "no_agent_assignee"
+      : null,
+  };
+}
+
 const SUCCESSFUL_RUN_HANDOFF_ACTIONS = [
   "issue.successful_run_handoff_required",
   "issue.successful_run_handoff_resolved",
@@ -2249,7 +2288,7 @@ export function issueRoutes(
     res.json({ ok: true });
   });
 
-  router.post("/companies/:companyId/issues", validate(createIssueSchema), async (req, res) => {
+  router.post("/companies/:companyId/issues", applyCreateIssueStatusDefault, validate(createIssueSchema), async (req, res) => {
     const companyId = req.params.companyId as string;
     assertCompanyAccess(req, companyId);
     assertNoAgentHostWorkspaceCommandMutation(req, collectIssueWorkspaceCommandPaths(req.body));
@@ -2289,6 +2328,7 @@ export function issueRoutes(
       details: {
         title: issue.title,
         identifier: issue.identifier,
+        ...buildCreateIssueActivityStatusDetails(issue, res),
         ...(Array.isArray(req.body.blockedByIssueIds) ? { blockedByIssueIds: req.body.blockedByIssueIds } : {}),
         ...summarizeIssueReferenceActivityDetails({
           addedReferencedIssues: referenceDiff.addedReferencedIssues.map(summarizeIssueRelationForActivity),
@@ -2338,7 +2378,7 @@ export function issueRoutes(
     });
   });
 
-  router.post("/issues/:id/children", validate(createChildIssueSchema), async (req, res) => {
+  router.post("/issues/:id/children", applyCreateIssueStatusDefault, validate(createChildIssueSchema), async (req, res) => {
     const parentId = req.params.id as string;
     const parent = await svc.getById(parentId);
     if (!parent) {
@@ -2380,6 +2420,7 @@ export function issueRoutes(
         parentId: parent.id,
         identifier: issue.identifier,
         title: issue.title,
+        ...buildCreateIssueActivityStatusDetails(issue, res),
         inheritedExecutionWorkspaceFromIssueId: parent.id,
         ...(Array.isArray(req.body.blockedByIssueIds) ? { blockedByIssueIds: req.body.blockedByIssueIds } : {}),
         ...(parentBlockerAdded ? { parentBlockerAdded: true } : {}),