feat(web/ui): rework project pane into flat list with repo/workspace/tool hierarchy

- Add ProjectListItem component with project header actions
- Show repositories horizontally with branch labels
- List workspaces vertically under each repo
- Show running tools per workspace from useSessions
- Link workspace names to /workspaces/:id
- Link tool names to web URL or terminal page
- Keep existing mobile view and dialogs unchanged

openspec/tasks/project-pane-rework.md

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+# OpenSpec Tasks: Project Pane Rework
+
+## Change
+`project-pane-rework`
+
+## Parent Spec
+`openspec/specs/project-pane-rework.md`
+
+## Status
+tasks
+
+---
+
+## Implementation Tasks
+
+- [ ] 1. Create `apps/web/src/components/features/project/ProjectListItem.tsx`
+  - Project header with name, description, Edit/Delete buttons
+  - Horizontal repo list using `ProjectRepoItem` helper
+  - Vertical workspace/tool lists using `SessionToolLink` helper
+  - Match running sessions from `useSessions` to workspaces/repos/projects
+
+- [ ] 2. Update `apps/web/src/pages/ProjectsPage.tsx`
+  - Import `ProjectListItem` and `useSessions`
+  - Replace desktop `ProjectCard` map with `ProjectListItem` map
+  - Remove unused `expandedProject` state and toggle logic from desktop view
+  - Keep mobile view and dialogs unchanged
+
+- [ ] 3. Add CSS to `apps/web/src/styles/pages/projects.css`
+  - `.project-list`
+  - `.project-list-item`
+  - `.project-list-item-header`
+  - `.project-list-item-title`
+  - `.project-list-item-actions`
+  - `.project-repo-list`
+  - `.project-repo-item`
+  - `.project-repo-item-header`
+  - `.project-repo-name`
+  - `.project-repo-branch`
+  - `.project-repo-workspaces`
+  - `.project-repo-workspace`
+  - `.workspace-name`
+  - `.workspace-tool-list`
+  - `.workspace-tool-link`
+  - `.session-status-dot`
+  - `.tool-name`
+
+- [ ] 4. Verification
+  - Run `cd apps/web && npm run typecheck`
+  - Run `cd apps/web && npm run lint`
+  - Spot-check desktop Projects page
+  - Test workspace and tool links
+  - Verify mobile view still works
+
+- [ ] 5. Update OpenSpec artifacts
+  - Mark tasks complete
+  - Add final report note
+
+---
+
+## Acceptance Criteria
+
+- All tasks above are completed.
+- `npm run typecheck` passes.
+- `npm run lint` passes.
+- Desktop Projects page shows the new flat list layout.
+- Each project header has name + Edit + Delete.
+- Repositories are horizontal.
+- Each repo shows name + branch.
+- Workspaces and running tools are listed vertically under each repo.
+- Workspace links navigate to `/workspaces/:workspaceId`.
+- Tool links open the tool.
+- Mobile view remains functional.
+
+---
+
+## Notes
+
+- Do not change backend APIs or data models.
+- Keep mobile behavior unchanged.
+- Prefer one commit per major area (component, page integration, CSS).