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/rename-prefix.md

@@ -0,0 +1,24 @@
+---
+description: Rename the issue prefix for all issues
+argument-hint: <new-prefix> [--dry-run]
+---
+
+Rename the issue prefix for all issues in the database.
+
+Updates all issue IDs and all text references across all fields.
+
+## Prefix Rules
+
+- Max length: 8 characters
+- Allowed: lowercase letters, numbers, hyphens
+- Must start with a letter
+- Must end with a hyphen (e.g., 'kw-', 'work-')
+
+## Usage
+
+- **Preview**: `bd rename-prefix kw- --dry-run`
+- **Apply**: `bd rename-prefix kw-`
+
+Example: Rename from 'knowledge-work-' to 'kw-'
+
+All dependencies and text references are automatically updated.