feat(completion): optimize ID prefix filtering and add completions to more commands

Improvements to shell completions from PR #935:

1. Add IDPrefix field to IssueFilter for efficient database-level filtering
   - Queries are now filtered at SQL level instead of fetching all issues
   - Updated sqlite, transaction, and memory stores to support IDPrefix

2. Add ValidArgsFunction to additional commands:
   - dep (add, remove, list, tree)
   - comments, comment (add)
   - delete
   - graph
   - label (add, remove, list)
   - duplicate, supersede
   - audit
   - move
   - relate, unrelate
   - refile
   - gate (show, resolve, add-waiter)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Executed-By: beads/crew/dave
Rig: beads
Role: crew

internal/types/types.go

@@ -758,7 +758,8 @@ type IssueFilter struct {
 	Labels      []string  // AND semantics: issue must have ALL these labels
 	LabelsAny   []string  // OR semantics: issue must have AT LEAST ONE of these labels
 	TitleSearch string
-	IDs         []string  // Filter by specific issue IDs
+	IDs         []string // Filter by specific issue IDs
+	IDPrefix    string   // Filter by ID prefix (for shell completion)
 	Limit       int
 	
 	// Pattern matching