Restore bd edit command and close duplicate issues

- Restore bd edit command (lost in 671b966 --no-db refactor)
- Document in AGENTS.md with 'HUMANS ONLY' warning
- Close duplicate issues: bd-129, bd-150, bd-144, bd-173/178/180
- Resolve import collisions: 8 issues remapped to new IDs

Amp-Thread-ID: https://ampcode.com/threads/T-e4780c42-9a6e-4021-8f8e-120b26562c2d
Co-authored-by: Amp <amp@ampcode.com>

AGENTS.md

@@ -151,6 +151,13 @@ bd create -f feature-plan.md --json
 bd update <id> [<id>...] --status in_progress --json
 bd update <id> [<id>...] --priority 1 --json
 
+# Edit issue fields in $EDITOR (HUMANS ONLY - not for agents)
+bd edit <id>                    # Edit description
+bd edit <id> --title            # Edit title
+bd edit <id> --design           # Edit design notes
+bd edit <id> --notes            # Edit notes
+bd edit <id> --acceptance       # Edit acceptance criteria
+
 # Link discovered work (old way)
 bd dep add <discovered-id> <parent-id> --type discovered-from