Implement urgency system with TaskWarrior-inspired calculation

- Add urgency calculation based on multiple factors:
  * Due date (linear scale: overdue=12.0, today=10.0, week=6.0, 2weeks=2.0)
  * Priority (H=6.0, M=3.9, D=1.8, L=0.0)
  * Age (0-2.0 over 365 days)
  * Active status (+4.0 boost)
  * Waiting status (-3.0 penalty)
  * Tags (+1.0 with count modifier)
  * Project assignment (+1.0)
  * Configurable urgent tag (default 'next', +15.0)

- Replace priority column with urgency in all reports
  * Display as decimal with 1 decimal place
  * 4-tier color coding: ≥10 (bright red), ≥5 (red), ≥2 (yellow), <2 (cyan)
  * Minimal format color-coded by urgency

- Add default urgency sorting to all reports
  * list, minimal, active, ready, overdue reports sort by urgency
  * newest/oldest keep date-based sorting

- Implement 'next' report
  * Shows most urgent ready tasks
  * Configurable limit (default 5)
  * Only includes tasks ready to work on (no future wait/scheduled)

- Add urgency display to info command
  * Shows urgency score alongside priority

- All urgency coefficients configurable via config
  * Adjusted defaults for Opal's simpler model (no blocking/annotations)
  * Configurable urgent tag name (not hardcoded to 'next')

Priority order maintained: High > Medium > Default > Low

opal-task/cmd/root.go

@@ -31,7 +31,7 @@ var commandNames = []string{
 // Report names (dynamically populated)
 var reportNames = []string{
 	"active", "all", "completed", "list", "minimal",
-	"newest", "oldest", "overdue", "ready", "recurring",
+	"newest", "next", "oldest", "overdue", "ready", "recurring",
 	"template", "waiting",
 }