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/epic.md

@@ -0,0 +1,26 @@
+---
+description: Epic management commands
+argument-hint: [command]
+---
+
+Manage epics (large features composed of multiple issues).
+
+## Available Commands
+
+- **status**: Show epic completion status
+  - Shows progress for each epic
+  - Lists child issues and their states
+  - Calculates completion percentage
+
+- **close-eligible**: Close epics where all children are complete
+  - Automatically closes epics when all child issues are done
+  - Useful for bulk epic cleanup
+
+## Epic Workflow
+
+1. Create epic: `bd create "Large Feature" -t epic -p 1`
+2. Link subtasks: `bd dep add bd-10 bd-20 --type parent-child` (epic bd-10 is parent of task bd-20)
+3. Track progress: `bd epic status`
+4. Auto-close when done: `bd epic close-eligible`
+
+Epics use parent-child dependencies to track subtasks.