docs(18-02): complete sidebar rebuild plan summary

- Rebuilt DashboardSidebar with GENERAL/PROJECTS sections and collapse button
- Updated sidebarPrimaryNavItems to Figma-spec 5 items
- Added sidebar-is-collapsed CSS rules and regenerated tailwind.css

.planning/phases/18-app-shell-navigation/18-02-SUMMARY.md

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+---
+phase: 18-app-shell-navigation
+plan: "02"
+subsystem: templates/css
+tags: [go, templ, sidebar, nav, css, collapse]
+dependency_graph:
+  requires: [18-01]
+  provides: [rebuilt DashboardSidebar with GENERAL/PROJECTS sections, sidebar collapse toggle, is-collapsed CSS rules]
+  affects: [backend/templates/app_layout.templ, backend/templates/app_layout_helpers.go, backend/internal/web/ui/app.css, backend/static/tailwind.css]
+tech_stack:
+  added: []
+  patterns: [inline JS onclick toggle, CSS class-driven collapse state, sidebar section labels]
+key_files:
+  created: []
+  modified:
+    - backend/templates/app_layout.templ
+    - backend/templates/app_layout_helpers.go
+    - backend/internal/web/ui/app.css
+    - backend/static/tailwind.css
+decisions:
+  - Inline JS onclick on collapse button (no Alpine.js, no server round-trip — state resets on reload per D-09)
+  - sidebar-is-collapsed toggled on .dashboard-shell wrapper (not on .dashboard-sidebar child) — correct for CSS grid column targeting per Research Pitfall 3
+  - PROJECTS section inlined directly in DashboardSidebar (SidebarProjectsSection component kept in file but no longer called)
+  - SidebarOrganizationFooter removed from DashboardSidebar call (moves to avatar dropdown in Plan 03)
+metrics:
+  duration: ~10min
+  completed: "2026-05-17"
+  tasks: 3
+  files: 4
+---
+
+# Phase 18 Plan 02: Sidebar Rebuild Summary
+
+**One-liner:** Full HTML/CSS rebuild of DashboardSidebar to Figma spec — two-section structure (GENERAL + PROJECTS), 5-item nav replacing old 5-item set, collapse toggle via inline JS, collapsed-state CSS rules in app.css + regenerated tailwind.css.
+
+## Tasks Completed
+
+| # | Task | Commit | Files |
+|---|------|--------|-------|
+| 1 | Update sidebarPrimaryNavItems and add team icon | 2763fc1 | app_layout_helpers.go, app_layout.templ |
+| 2 | Rebuild DashboardSidebar HTML with sections and collapse button | b592a02 | app_layout.templ |
+| 3 | Add sidebar collapsed-state CSS and regenerate tailwind.css | 8a91183 | app.css, tailwind.css |
+
+## Decisions Made
+
+- **Inline JS onclick** on the collapse button — toggles `sidebar-is-collapsed` on `.dashboard-shell`; no Alpine.js dependency, no server round-trip, state resets on page reload per D-09
+- **Target `.dashboard-shell` for collapse CSS** — grid column must be controlled on the shell wrapper, not the sidebar child (per Research Pitfall 3)
+- **PROJECTS section inlined** into DashboardSidebar body rather than delegating to `SidebarProjectsSection` — keeps the new structure flat and avoids the HR separator; the standalone component remains in the file for Plan 03 cleanup
+- **SidebarOrganizationFooter no longer called** from DashboardSidebar — it moves to the avatar dropdown in Plan 03; component kept in file to avoid breaking Plan 03 which references it
+
+## Verification
+
+- `templ generate ./...` — zero errors
+- `go build ./...` — zero errors
+- `go test ./...` — all tests pass (backend/internal/web: 0.310s, backend/templates: 0.529s)
+- `grep -c "sidebar-is-collapsed" backend/static/tailwind.css` — returns 1
+- `grep "My Tasks\|Team Members" backend/templates/app_layout_helpers.go` — shows updated nav items
+
+## Deviations from Plan
+
+None — plan executed exactly as written.
+
+## Known Stubs
+
+- `SidebarOrganizationFooter` component exists in `app_layout.templ` but is no longer called from `DashboardSidebar`. Plan 03 will repurpose or remove it when building the avatar dropdown.
+- `SidebarProjectsSection` component exists but is no longer called; Plan 03 will clean up.
+- The `DividerAfter` field on `sidebarNavItem` struct is unused (kept for zero-diff struct compatibility); can be removed in a later cleanup.
+
+## Threat Flags
+
+None — tablo.Color.String is user's own data interpolated into a `style` attribute, which is acceptable per T-18-02-01 disposition. CSS artifact edit-path enforced (app.css → tailwind.css pipeline, never direct edit of tailwind.css).
+
+## Self-Check: PASSED
+
+- `backend/templates/app_layout.templ` — exists, DashboardSidebar has GENERAL/PROJECTS sections and collapse button
+- `backend/templates/app_layout_helpers.go` — exists, sidebarPrimaryNavItems returns 5 items with Home/My Tasks/Projects/Events/Team Members
+- `backend/internal/web/ui/app.css` — exists, contains sidebar-is-collapsed block
+- `backend/static/tailwind.css` — exists, grep returns 1 for sidebar-is-collapsed
+- Commits 2763fc1, b592a02, 8a91183 — all present in git log