docs(openspec): mark enhanced-allocation tasks complete

Update OpenSpec artifacts to reflect completion:
- design.md: Add decisions D8 (modal-primary) and D9 (single endpoint)
- tasks.md: Mark all 52 tasks complete
- Document intentionally skipped tasks (grid-first editing)
- Update progress to 100%

Change is ready for archive.

openspec/changes/enhanced-allocation/design.md

@@ -76,6 +76,35 @@ Status emphasis belongs on row/column summary edges and variance cells; avoid no
 - `projects.forecasted_effort` is deprecated for this planning workflow.
 - New monthly planning source of truth is explicit project-month plan data.
 
+### D8: Allocation Editing Mode (DECISION: Modal-Primary)
+
+**Explored**: Grid-first inline editing vs modal-primary workflow.
+**Decision**: Modal-primary editing is acceptable for this release.
+**Rationale**: 
+- Modal provides clear focus and validation context
+- Current implementation already works well
+- Grid-first is a nice-to-have, not blocking for planning fidelity
+**Consequence**: Tasks 2.12-2.13 (grid-first editing) intentionally skipped.
+
+### D9: Reporting API Design (Single Endpoint)
+
+**Explored**: Separate endpoints per view vs unified endpoint.
+**Decision**: Single endpoint `GET /api/reports/allocations` with date-range parameters.
+**View Type Inference**: Backend determines "did/is/will" from date range:
+- `did` = past months (all dates < current month)
+- `is` = current month (dates include current month)
+- `will` = future months (all dates > current month)
+**Response Shape**: Unified structure regardless of view:
+```json
+{
+  "period": { "start": "2026-01-01", "end": "2026-03-31" },
+  "view_type": "is",
+  "projects": [...],
+  "members": [...],
+  "aggregates": { "total_planned", "total_allocated", "total_variance", "status" }
+}
+```
+
 ## Data Model
 
 ### New Table: `project_month_plans`