refactor(projects/sidebar): remove temp snapshot side-effects and simplify session metadata UX

Why this change was needed:
- Project listing had an implicit side effect: every fetch wrote a debug snapshot under `.tmp/project-dumps`.
  That added unnecessary disk I/O to a hot path, introduced hidden runtime behavior, and created maintenance
  overhead for code that was not part of product functionality.
- Keeping snapshot-specific exports/tests around made the projects module API broader than needed and coupled
  tests to temporary/debug behavior instead of user-visible behavior.
- Codex sessions could remain stuck with a placeholder name (`Untitled Codex Session`) even after a real title
  became available from newer sync data, which degraded session discoverability in the UI.
- Sidebar session rows showed duplicated provider branding and long-form relative times, which added visual noise
  and reduced scan speed when many sessions are listed.

What changed:
- Removed temporary projects snapshot dumping from `projects-with-sessions-fetch.service.ts`:
  - deleted snapshot types/helpers and file-write flow
  - removed the write call from `getProjectsWithSessions`
- Removed snapshot-related surface area from `projects/index.ts`.
- Removed the snapshot-focused test `projects.service.test.ts` that only validated removed debug behavior.
- Updated `codex-session-synchronizer.provider.ts` to upgrade session names when an existing session still has
  the placeholder title but a real parsed name is now available.
- Updated `SidebarSessionItem.tsx`:
  - removed duplicate provider logo rendering in each session row
  - moved age indicator to the right side
  - made age indicator fade on hover to prioritize action controls
  - switched to compact relative time format (`<1m`, `Xm`, `Xhr`, `Xd`) for faster list scanning

Outcome:
- Lower overhead and fewer hidden side effects in project fetches.
- Cleaner module boundaries in projects.
- Better Codex session naming consistency after sync.
- Cleaner sidebar density and clearer hover/action behavior.

server/modules/projects/tests/projects.service.test.ts

@@ -1,33 +0,0 @@
-import assert from 'node:assert/strict';
-import test from 'node:test';
-
-import {
-  createProjectsSnapshot,
-} from '@/modules/projects/index.js';
-import { ProjectListItem, ProjectsSnapshot } from '@/modules/projects/services/projects-with-sessions-fetch.service.js';
-
-test('createProjectsSnapshot returns an object matching the predefined snapshot type', () => {
-  const projects: ProjectListItem[] = [
-    {
-      projectId: 'project-1',
-      path: '/tmp/project-1',
-      displayName: 'project-1',
-      fullPath: '/tmp/project-1',
-      isStarred: false,
-      sessions: [],
-      cursorSessions: [],
-      codexSessions: [],
-      geminiSessions: [],
-      sessionMeta: {
-        hasMore: false,
-        total: 0,
-      },
-    },
-  ];
-
-  const snapshot: ProjectsSnapshot = createProjectsSnapshot(projects);
-
-  assert.equal(typeof snapshot.generatedAt, 'string');
-  assert.equal(snapshot.projectCount, 1);
-  assert.deepEqual(snapshot.projects, projects);
-});