docs(openspec): archive completed changes and sync main specs

Archive three completed changes to archive/:
- api-resource-standard (70 tasks, 14 resource classes)
- capacity-expert-mode (68 tasks, expert mode planning grid)
- enhanced-allocation (62 tasks, planning fidelity + reporting)

Sync all delta specs to main specs/:
- api-resource-standard: API response standardization
- capacity-expert-mode: Expert mode toggle, grid, KPIs, batch API
- resource-allocation: Month execution comparison, bulk, untracked
- untracked-allocation: Null team member support
- allocation-indicators: Variance indicators (red/amber/neutral)
- monthly-budget: Explicit project-month planning

All changes verified and tested (157 tests passing).

openspec/specs/untracked-allocation/spec.md

@@ -0,0 +1,49 @@
+# Purpose
+
+TBD
+
+# Requirements
+
+## Requirement: Support null team member in allocation APIs
+
+The system SHALL allow allocation records with `team_member_id = null`.
+
+### Scenario: Create untracked allocation
+- **GIVEN** user has allocation create permission
+- **WHEN** POST /api/allocations with `team_member_id = null`
+- **THEN** allocation is created successfully
+
+### Scenario: Bulk create with mixed tracked/untracked
+- **GIVEN** a bulk payload contains tracked and untracked entries
+- **WHEN** POST /api/allocations/bulk is executed
+- **THEN** untracked entries with valid data are processed successfully
+
+## Requirement: Include untracked in project totals
+
+Untracked hours SHALL contribute to project-level and grand totals.
+
+### Scenario: Project total includes untracked
+- **GIVEN** project has tracked 80h and untracked 20h in selected month
+- **WHEN** project row total is computed
+- **THEN** row total is 100h
+
+## Requirement: Exclude untracked from member capacity metrics
+
+Untracked allocations SHALL NOT contribute to any team member utilization/capacity variance.
+
+### Scenario: Member utilization ignores untracked
+- **GIVEN** selected month has untracked allocations
+- **WHEN** member column totals and capacity variance are computed
+- **THEN** untracked rows are excluded from member computations
+
+## Requirement: Present untracked in execution grid
+
+The allocation grid SHALL expose untracked as a first-class execution bucket.
+
+### Scenario: Untracked column visible
+- **WHEN** manager opens allocation execution grid
+- **THEN** untracked column/bucket is visible and editable
+
+## Requirement: Capacity validation
+
+Capacity validation SHALL be skipped for untracked allocations (`team_member_id = null`).