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/defer.go

@@ -4,9 +4,11 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"time"
 
 	"github.com/spf13/cobra"
 	"github.com/steveyegge/beads/internal/rpc"
+	"github.com/steveyegge/beads/internal/timeparsing"
 	"github.com/steveyegge/beads/internal/types"
 	"github.com/steveyegge/beads/internal/ui"
 	"github.com/steveyegge/beads/internal/utils"
@@ -25,12 +27,25 @@ be revisited.
 Deferred issues don't show in 'bd ready' but remain visible in 'bd list'.
 
 Examples:
-  bd defer bd-abc        # Defer a single issue
-  bd defer bd-abc bd-def # Defer multiple issues`,
+  bd defer bd-abc                  # Defer a single issue (status-based)
+  bd defer bd-abc --until=tomorrow # Defer until specific time
+  bd defer bd-abc bd-def           # Defer multiple issues`,
 	Args: cobra.MinimumNArgs(1),
 	Run: func(cmd *cobra.Command, args []string) {
 		CheckReadonly("defer")
 
+		// Parse --until flag (GH#820)
+		var deferUntil *time.Time
+		untilStr, _ := cmd.Flags().GetString("until")
+		if untilStr != "" {
+			t, err := timeparsing.ParseRelativeTime(untilStr, time.Now())
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "Error: invalid --until format %q. Examples: +1h, tomorrow, next monday, 2025-01-15\n", untilStr)
+				os.Exit(1)
+			}
+			deferUntil = &t
+		}
+
 		ctx := rootCtx
 
 		// Resolve partial IDs first
@@ -69,6 +84,11 @@ Examples:
 					ID:     id,
 					Status: &status,
 				}
+				// Add defer_until if --until specified (GH#820)
+				if deferUntil != nil {
+					s := deferUntil.Format(time.RFC3339)
+					updateArgs.DeferUntil = &s
+				}
 
 				resp, err := daemonClient.Update(updateArgs)
 				if err != nil {
@@ -108,6 +128,10 @@ Examples:
 			updates := map[string]interface{}{
 				"status": string(types.StatusDeferred),
 			}
+			// Add defer_until if --until specified (GH#820)
+			if deferUntil != nil {
+				updates["defer_until"] = *deferUntil
+			}
 
 			if err := store.UpdateIssue(ctx, fullID, updates, actor); err != nil {
 				fmt.Fprintf(os.Stderr, "Error deferring %s: %v\n", fullID, err)
@@ -136,5 +160,7 @@ Examples:
 }
 
 func init() {
+	// Time-based scheduling flag (GH#820)
+	deferCmd.Flags().String("until", "", "Defer until specific time (e.g., +1h, tomorrow, next monday)")
 	rootCmd.AddCommand(deferCmd)
 }