Implement Trello smart sorting by newest card activity

  - Update GetBoards SQL query with LEFT JOIN and GROUP BY
  - Sort by: 1) Has cards, 2) Newest card (MAX ID), 3) Board name
  - Update GetBoardsWithCards to match SQL sorting behavior
  - Leverage Trello ID chronological sortability (newer > older)
  - Active boards with recent activity appear first
  - All tests passing

  Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

4 files changed, 44 insertions, 8 deletions

diff --git a/PHASE_2_SURGICAL_PLAN.md b/PHASE_2_SURGICAL_PLAN.md
index e300639..bd761e5 100644
--- a/PHASE_2_SURGICAL_PLAN.md
+++ b/PHASE_2_SURGICAL_PLAN.md
@@ -43,7 +43,7 @@ Refactor the frontend and router to support 4 distinct tabs.
 ```
 
 ## 3. Trello: Smart Sorting & Logic
-**Status:** [ ] Pending
+**Status:** [x] Complete
 
 ```text
 Enhance Trello sorting in `internal/api/trello.go` and `internal/store/sqlite.go`.
diff --git a/SESSION_STATE.md b/SESSION_STATE.md
index dd8e30f..4c03fb2 100644
--- a/SESSION_STATE.md
+++ b/SESSION_STATE.md
@@ -51,6 +51,13 @@ Frontend modernization with tabs, HTMX, and Tailwind build pipeline complete.
   - web/templates/partials/planning-tab.html: New tab for Trello boards
   - web/templates/partials/meals-tab.html: New tab for PlanToEat meals
   - Clean separation of concerns: Tasks (due items), Planning (all boards), Notes (knowledge), Meals (calendar)
+- **Trello Smart Sorting:** Activity-based board ordering by newest card
+  - internal/store/sqlite.go:426-438: Updated GetBoards SQL query with LEFT JOIN and GROUP BY
+  - Sort order: 1) Has cards (COUNT > 0), 2) Newest card (MAX(c.id) DESC), 3) Board name (ASC)
+  - internal/api/trello.go:220-254: Updated GetBoardsWithCards sorting logic
+  - Finds maximum card ID in each board (Trello IDs are chronologically sortable)
+  - Active boards with recent activity appear first, inactive boards at bottom
+  - All tests passing (go test ./...)
   - **Build Pipeline:** npm + PostCSS + Tailwind configuration (replaced CDN)
     - package.json, tailwind.config.js, postcss.config.js, Makefile
     - Custom design system with brand colors (Trello, Todoist, Obsidian, PlanToEat)
@@ -94,9 +101,8 @@ Frontend modernization with tabs, HTMX, and Tailwind build pipeline complete.
 - **Decision:** Unified Atom Model - Abstract all data sources (Trello, Todoist, Obsidian, PlanToEat) into a single `models.Atom` type for consistent handling, sorting, and rendering across the UI.
 
 ## 📋 Next Steps
-1. **Phase 2 Step 3:** Trello smart sorting (activity-based, modification date).
-2. **Phase 2 Step 4:** Todoist "due first" sorting.
-3. **Phase 2 Remaining:** Obsidian search & categorization, visual overhaul (glassmorphism), write operations, PWA.
+1. **Phase 2 Step 4:** Todoist "due first" sorting.
+2. **Phase 2 Remaining:** Obsidian search & categorization, visual overhaul (glassmorphism), write operations, PWA.
 
 ## ⚠️ Known Blockers / Debt
 - None currently.
diff --git a/internal/api/trello.go b/internal/api/trello.go
index b9391d6..c78ebc8 100644
--- a/internal/api/trello.go
+++ b/internal/api/trello.go
@@ -217,13 +217,39 @@ func (c *TrelloClient) GetBoardsWithCards(ctx context.Context) ([]models.Board,
 
 	wg.Wait()
 
-	// Sort boards: Non-empty boards first, then alphabetical by name
+	// Sort boards: Non-empty boards first, newest card activity, then alphabetical by name
+	// Trello card IDs are chronologically sortable (newer IDs > older IDs)
 	sort.Slice(boards, func(i, j int) bool {
 		hasCardsI := len(boards[i].Cards) > 0
 		hasCardsJ := len(boards[j].Cards) > 0
+
+		// 1. Prioritize boards with cards
 		if hasCardsI != hasCardsJ {
 			return hasCardsI // true (non-empty) comes before false
 		}
+
+		// 2. If both have cards, compare by newest card (max ID)
+		if hasCardsI && hasCardsJ {
+			maxIDI := ""
+			for _, card := range boards[i].Cards {
+				if maxIDI == "" || card.ID > maxIDI {
+					maxIDI = card.ID
+				}
+			}
+
+			maxIDJ := ""
+			for _, card := range boards[j].Cards {
+				if maxIDJ == "" || card.ID > maxIDJ {
+					maxIDJ = card.ID
+				}
+			}
+
+			if maxIDI != maxIDJ {
+				return maxIDI > maxIDJ // Newer (larger) ID comes first
+			}
+		}
+
+		// 3. Fallback to alphabetical by name
 		return boards[i].Name < boards[j].Name
 	})
 
diff --git a/internal/store/sqlite.go b/internal/store/sqlite.go
index 5063336..fa8f2b1 100644
--- a/internal/store/sqlite.go
+++ b/internal/store/sqlite.go
@@ -424,13 +424,17 @@ func (s *Store) SaveBoards(boards []models.Board) error {
 
 // GetBoards retrieves all boards with their cards from the database
 func (s *Store) GetBoards() ([]models.Board, error) {
-	// Fetch boards, sorted by: non-empty boards first, then alphabetical
+	// Fetch boards, sorted by: non-empty boards first, newest card activity, then alphabetical
+	// Trello card IDs are chronologically sortable (newer IDs > older IDs)
 	boardRows, err := s.db.Query(`
 		SELECT b.id, b.name
 		FROM boards b
+		LEFT JOIN cards c ON c.board_id = b.id
+		GROUP BY b.id, b.name
 		ORDER BY
-			CASE WHEN (SELECT COUNT(*) FROM cards c WHERE c.board_id = b.id) > 0 THEN 0 ELSE 1 END,
-			b.name
+			CASE WHEN COUNT(c.id) > 0 THEN 0 ELSE 1 END,
+			MAX(c.id) DESC,
+			b.name ASC
 	`)
 	if err != nil {
 		return nil, err