Add command documentation and improve daemon UX

- Added human-readable uptime formatting (51m 59s vs 3119.4 seconds)
- Fixed daemon stop race condition with SIGKILL
- Added markdown docs for 19 commands: blocked, comments, compact, daemon,
  delete, dep, epic, export, import, label, list, quickstart, rename-prefix,
  renumber, reopen, repos, restore, stale, sync
- Closed: bd-159, bd-152, bd-168
- Deleted test issues: bd-144, bd-145

Amp-Thread-ID: https://ampcode.com/threads/T-9f7c3fed-62de-4bcd-a059-8c1b77cdb841
Co-authored-by: Amp <amp@ampcode.com>

commands/renumber.md

@@ -0,0 +1,29 @@
+---
+description: Renumber all issues sequentially
+argument-hint: [--dry-run] [--force]
+---
+
+Renumber all issues sequentially to eliminate gaps in the ID space.
+
+## What It Does
+
+- Renumber all issues starting from 1 (keeps chronological order)
+- Update all dependency links (all types)
+- Update all text references in descriptions, notes, acceptance criteria
+- Show mapping report: old ID -> new ID
+- Export updated database to JSONL
+
+## Usage
+
+- **Preview**: `bd renumber --dry-run`
+- **Apply**: `bd renumber --force`
+
+## Risks
+
+⚠️ **Warning**: This operation cannot be undone!
+
+- May break external references in GitHub issues, docs, commits
+- Git history may become confusing
+- Backup recommended before running
+
+Use sparingly - only when ID gaps are problematic.