Information Architecture + project/agent visual refresh (experimental) (#7543)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work.
> - The board UI is the control surface for issues, projects, agents,
goals, workspaces, and operator settings.
> - The existing navigation and list surfaces make several
high-frequency workflows feel harder to scan than they should,
especially around projects and agents.
> - The product direction is to improve those surfaces without breaking
the existing route model or forcing a new IA on every operator at once.
> - This pull request now keeps the dependent IA, project identity, and
agent-list visual refresh work together while the Issue-to-Task copy
migration is split into #7651.
> - The benefit is a clearer left nav, better project identity, denser
agent/project list rows, and brand-aligned status treatment while
preserving the classic default experience behind a flag.

## Linked Issues or Issue Description

Refs #7645
Refs #7651

Internal planning/work references: PAP-53, PAP-56, PAP-58, PAP-59,
PAP-60, PAP-61, PAP-68, PAP-69, PAP-70, PAP-71, PAP-72, PAP-75, PAP-76,
PAP-80, PAP-85, PAP-86, PAP-87, PAP-88, PAP-89.

## What Changed

- Adds `enableStreamlinedLeftNavigation`, defaulting off, and gates
sidebar presentation so classic navigation remains the default.
- Adds project icon persistence, validation, portability, picker UI, and
`ProjectTile` rendering while defaulting new projects to neutral gray.
- Adds projects-list task-count and budget summary data with focused
server/shared/UI coverage.
- Refreshes agent list rows, row actions, active/recent sidebar
behavior, and status capsule/chip styling for the approved brand state
system.
- Removes the placeholder Conference room and Artifacts nav/routes from
the finalized experimental nav direction.
- Removes `pnpm-lock.yaml` and the Issue-to-Task copy migration from
this PR diff; the copy migration now lives in #7651.

## Verification

- Existing branch verification from the authored commits: UI typecheck,
targeted unit tests, and light/dark visual checks for `/agents`, agent
detail, and design-guide status states.
- Maintainer cleanup verification on `75e34e5`: `git diff --check
origin/master...HEAD` passed, the `design/` diff is empty, and the PR
diff is 61 files, below Greptile's 100-file review limit.
- `pnpm --filter @paperclipai/ui build` passed.
- `NODE_ENV=test pnpm exec vitest run
ui/src/components/Sidebar.test.tsx` passed: 1 file, 8 tests.
- CI and Greptile should rerun on the latest push.

## Risks

- Broad UI surface area: the experimental flag keeps the classic nav
default, but changed shared components such as `EntityRow`,
`ProjectTile`, and agent status badges could affect multiple pages.
- Database migration: `projects.icon` is additive and nullable, but
migration ordering and portability import/export must stay aligned.
- The Issue-to-Task copy migration is now separated into #7651, so
reviewers should evaluate this PR as IA/project/agent presentation work
only.
- Visual regressions are possible across smaller widths because the PR
intentionally changes dense list-row layouts.

## Model Used

Claude Opus 4.8 assisted the original feature commits.
Paperclip-Paperclip agents assisted some planning/design commits. Codex
/ GPT-5-class coding agent with shell, GitHub CLI, and repository access
performed this PR-readiness cleanup and split.

## 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: Paperclip <noreply@paperclip.ing>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Dotta <bippadotta@protonmail.com>

ui/src/pages/Agents.test.tsx

@@ -126,7 +126,11 @@ describe("Agents", () => {
     });
 
     mockAgentsApi.list.mockResolvedValue([
-      makeAgent({ adapterConfig: { model: "gpt-5.4" } }),
+      makeAgent({
+        adapterConfig: { model: "gpt-5.4" },
+        // Old enough that relativeTime() falls back to an absolute date string.
+        lastHeartbeatAt: new Date("2026-01-15T00:00:00Z"),
+      }),
     ]);
     mockAgentsApi.org.mockResolvedValue([
       {
@@ -180,5 +184,44 @@ describe("Agents", () => {
 
     expect(container.textContent).toContain("codex_local");
     expect(container.textContent).toContain("gpt-5.4");
+
+    // The heartbeat cell must render on a single line so full dates like
+    // "Apr 30, 2026" never wrap (PAP-85 defect #2).
+    const heartbeatCell = container.querySelector(".whitespace-nowrap.w-24");
+    expect(heartbeatCell).not.toBeNull();
+    expect(heartbeatCell?.textContent).not.toContain("\n");
+  });
+
+  it("gives list-view rows a fixed-width title so meta columns align (PAP-86)", async () => {
+    root = createRoot(container);
+    await act(async () => {
+      root!.render(
+        <QueryClientProvider client={queryClient}>
+          <ToastProvider>
+            <Agents />
+          </ToastProvider>
+        </QueryClientProvider>,
+      );
+    });
+    await flushReact();
+    await flushReact();
+
+    // Switch from the default org view to the list view.
+    const listToggle = Array.from(container.querySelectorAll("button")).find(
+      (btn) => btn.querySelector("svg.lucide-list"),
+    );
+    expect(listToggle).toBeDefined();
+    await act(async () => {
+      listToggle!.click();
+    });
+    await flushReact();
+
+    // The title cell carries a constant width (`w-56`), not a content-sized
+    // `min-w-[7rem]`, so the `meta` group starts at the same x on every row and
+    // the model + timestamp columns line up vertically.
+    const titleCell = container.querySelector(".w-56");
+    expect(titleCell).not.toBeNull();
+    expect(titleCell?.textContent).toContain("Alpha");
+    expect(container.querySelector(".min-w-\\[7rem\\]")).toBeNull();
   });
 });