[codex] Add blocked inbox attention view (#5603)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies through
company-scoped issues, comments, approvals, and execution workspaces.
> - Operators need the Inbox to show not only active work, but also
blocked work that may need human or agent attention.
> - The existing inbox experience did not have a dedicated blocked-work
surface, so blocked tasks were harder to triage and resume deliberately.
> - Backend consumers also needed a compact attention signal that
distinguishes actionable blockers from covered or waiting blocker
states.
> - This pull request adds a Blocked Inbox tab backed by issue
blocker-attention metadata, shared validators, and UI helpers.
> - The benefit is a clearer triage path for stalled or blocked
Paperclip work without exposing external wait internals in the
operator-facing UI.

## What Changed

- Added shared issue blocker-attention types, validators, and exports
for the API/UI contract.
- Added backend blocker-attention computation and issue route support
for blocked inbox data.
- Added the Blocked Inbox tab, blocked reason chips, filtering/search
UI, responsive layouts, and Storybook stories.
- Updated inbox helpers and page behavior so toolbar controls only
appear where they apply.
- Added coverage for shared validators, server blocker-attention
behavior, blocked inbox UI helpers/components, and the Inbox page.
- Added a screenshot helper script for the blocked inbox Storybook
stories.
- Addressed Greptile feedback by making urgency sorting deterministic
for null stop times, avoiding full blocked-inbox list enrichment for
counts, and hardening the screenshot helper.

## Verification

- Rebased the branch cleanly onto `public-gh/master`.
- Confirmed the diff does not include `pnpm-lock.yaml`.
- Confirmed the diff does not include database migration files.
- Ran `pnpm exec vitest run packages/shared/src/validators/issue.test.ts
server/src/__tests__/issue-blocker-attention.test.ts
ui/src/components/BlockedInboxView.test.tsx
ui/src/components/BlockedReasonChip.test.tsx
ui/src/lib/blockedInbox.test.ts ui/src/lib/inbox.test.ts
ui/src/pages/Inbox.test.tsx`.
- Ran `pnpm --filter @paperclipai/shared typecheck && pnpm --filter
@paperclipai/server typecheck && pnpm --filter @paperclipai/ui
typecheck`.
- Checked `ROADMAP.md`; this is scoped inbox/operator triage work and
does not duplicate a listed roadmap feature.
- Greptile Review is green on the latest head and all four Greptile
review threads are resolved.
- GitHub PR checks are green on the latest head: policy, security/snyk,
e2e, verify, Canary Dry Run, Greptile Review, and serialized server
suites 1/4 through 4/4.

## Risks

- Medium review surface because this touches the shared issue contract,
server issue services, and the Inbox UI together.
- Blocker-attention classification may need product tuning after
operators use it on real blocked queues.
- UI screenshots were not attached in this PR-opening pass; the branch
includes `scripts/screenshot-blocked-inbox.mjs` and Storybook stories
for visual capture.

> 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, GPT-5-based coding agent with shell, git, GitHub CLI,
GitHub connector, and Paperclip API tool use. Reasoning mode: medium.
Context window: 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
- [ ] 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>

ui/src/lib/inbox.ts

@@ -25,7 +25,7 @@ export const INBOX_NESTING_KEY = "paperclip:inbox:nesting";
 export const INBOX_GROUP_BY_KEY = "paperclip:inbox:group-by";
 export const INBOX_FILTER_PREFERENCES_KEY_PREFIX = "paperclip:inbox:filters";
 export const INBOX_COLLAPSED_GROUPS_KEY_PREFIX = "paperclip:inbox:collapsed-groups";
-export type InboxTab = "mine" | "recent" | "unread" | "all";
+export type InboxTab = "mine" | "recent" | "unread" | "blocked" | "all";
 export type InboxCategoryFilter =
   | "everything"
   | "issues_i_touched"
@@ -630,7 +630,13 @@ export function resolveInboxNestingEnabled(preferenceEnabled: boolean, isMobile:
 export function loadLastInboxTab(): InboxTab {
   try {
     const raw = localStorage.getItem(INBOX_LAST_TAB_KEY);
-    if (raw === "all" || raw === "unread" || raw === "recent" || raw === "mine") return raw;
+    if (
+      raw === "all"
+      || raw === "unread"
+      || raw === "recent"
+      || raw === "mine"
+      || raw === "blocked"
+    ) return raw;
     if (raw === "new") return "mine";
     return "mine";
   } catch {