feat(dates): add --due and --defer timestamp options with natural language parsing (#847)

* feat(dates): add due date schema and --due flag

- Add due_at and defer_until columns to issues table via migration 035
- Implement --due flag on create command with ISO date parsing
- Extend RPC protocol and daemon to pass DueAt from CLI to storage
- Display DueAt and DeferUntil in show command output
- Update Issue type with new date fields

Users can now set due dates when creating issues, enabling deadline-based
task management.

* feat(dates): add compact duration parser (+6h, +1d, +2w)

- Create internal/timeparsing package with layered parser architecture
- Implement parseCompactDuration with regex pattern [+-]?\d+[hdwmy]
- Add comprehensive test suite (22 cases) for duration parsing
- Integrate into create.go with fallback to ISO format

Supports hours (h), days (d), weeks (w), months (m), and years (y).
Negative values allowed for past dates.

* feat(dates): add NLP parsing for natural language dates

Integrate olebedev/when library for natural language time expressions.
The layered parser now handles: compact duration → absolute formats → NLP.

Changes:
- Add olebedev/when dependency for NLP parsing
- Implement ParseNaturalLanguage and ParseRelativeTime functions
- Reorder layers: absolute formats before NLP to avoid misinterpretation
- Simplify create.go to use unified ParseRelativeTime
- Add comprehensive NLP test coverage (22 test cases)

Supports: tomorrow, next monday, in 3 days, 3 days ago

* feat(dates): add --defer flag to create/update/defer commands

Add time-based deferral support alongside existing status-based defer.
Issues can now be hidden from bd ready until a specific time.

Changes:
- Add --defer flag to bd create (sets defer_until on creation)
- Add --due and --defer flags to bd update (modify existing issues)
- Add --until flag to bd defer (combines status=deferred with defer_until)
- Add DueAt/DeferUntil fields to UpdateArgs in protocol.go

Supports: +1h, tomorrow, next monday, 2025-01-15

* feat(dates): add defer_until filtering to ready command

Add time-based deferral support to bd ready:

- Add --include-deferred flag to show issues with future defer_until
- Filter out issues where defer_until > now by default
- Update undefer to clear defer_until alongside status change
- Add IncludeDeferred to WorkFilter and RPC ReadyArgs

Part of GH#820: Relative Date Parsing (Phase 5)

* feat(dates): add polish and tests for relative date parsing

Add user-facing warnings when defer date is in the past to help catch
common mistakes. Expand help text with format examples and document
the olebedev/when September parsing quirk.

Tests:
- TestCreateSuite/WithDueAt, WithDeferUntil, WithBothDueAndDefer
- TestReadyWorkDeferUntil (ExcludesFutureDeferredByDefault, IncludeDeferredShowsAll)

Docs:
- CLAUDE.md quick reference updated with new flags
- Help text examples for --due, --defer on create/update

Closes: Phase 6 of beads-820-relative-dates spec

* feat(list): add time-based query filters for defer/due dates

Add --deferred, --defer-before, --defer-after, --due-before, --due-after,
and --overdue flags to bd list command. All date filters now support
relative time expressions (+6h, tomorrow, next monday) via the
timeparsing package.

Filters:
- --deferred: issues with defer_until set
- --defer-before/after: filter by defer_until date range
- --due-before/after: filter by due_at date range
- --overdue: due_at in past AND status != closed

Existing date filters (--created-after, etc.) now also support relative
time expressions through updated parseTimeFlag().

* build(nix): update vendorHash for olebedev/when dependency

The olebedev/when library was added for natural language date parsing
(GH#820). This changes go.sum, requiring an updated vendorHash in the
Nix flake configuration.

cmd/bd/ready.go

@@ -43,6 +43,7 @@ This is useful for agents executing molecules to see which steps can run next.`,
 		parentID, _ := cmd.Flags().GetString("parent")
 		molTypeStr, _ := cmd.Flags().GetString("mol-type")
 		prettyFormat, _ := cmd.Flags().GetBool("pretty")
+		includeDeferred, _ := cmd.Flags().GetBool("include-deferred")
 		var molType *types.MolType
 		if molTypeStr != "" {
 			mt := types.MolType(molTypeStr)
@@ -67,12 +68,13 @@ This is useful for agents executing molecules to see which steps can run next.`,
 
 		filter := types.WorkFilter{
 			// Leave Status empty to get both 'open' and 'in_progress'
-			Type:       issueType,
-			Limit:      limit,
-			Unassigned: unassigned,
-			SortPolicy: types.SortPolicy(sortPolicy),
-			Labels:     labels,
-			LabelsAny:  labelsAny,
+			Type:            issueType,
+			Limit:           limit,
+			Unassigned:      unassigned,
+			SortPolicy:      types.SortPolicy(sortPolicy),
+			Labels:          labels,
+			LabelsAny:       labelsAny,
+			IncludeDeferred: includeDeferred, // GH#820: respect --include-deferred flag
 		}
 		// Use Changed() to properly handle P0 (priority=0)
 		if cmd.Flags().Changed("priority") {
@@ -96,15 +98,16 @@ This is useful for agents executing molecules to see which steps can run next.`,
 		// If daemon is running, use RPC
 		if daemonClient != nil {
 			readyArgs := &rpc.ReadyArgs{
-				Assignee:   assignee,
-				Unassigned: unassigned,
-				Type:       issueType,
-				Limit:      limit,
-				SortPolicy: sortPolicy,
-				Labels:     labels,
-				LabelsAny:  labelsAny,
-				ParentID:   parentID,
-				MolType:    molTypeStr,
+				Assignee:        assignee,
+				Unassigned:      unassigned,
+				Type:            issueType,
+				Limit:           limit,
+				SortPolicy:      sortPolicy,
+				Labels:          labels,
+				LabelsAny:       labelsAny,
+				ParentID:        parentID,
+				MolType:         molTypeStr,
+				IncludeDeferred: includeDeferred, // GH#820
 			}
 			if cmd.Flags().Changed("priority") {
 				priority, _ := cmd.Flags().GetInt("priority")
@@ -447,6 +450,7 @@ func init() {
 	readyCmd.Flags().String("parent", "", "Filter to descendants of this bead/epic")
 	readyCmd.Flags().String("mol-type", "", "Filter by molecule type: swarm, patrol, or work")
 	readyCmd.Flags().Bool("pretty", false, "Display issues in a tree format with status/priority symbols")
+	readyCmd.Flags().Bool("include-deferred", false, "Include issues with future defer_until timestamps")
 	rootCmd.AddCommand(readyCmd)
 	blockedCmd.Flags().String("parent", "", "Filter to descendants of this bead/epic")
 	rootCmd.AddCommand(blockedCmd)