docs: sync to Claude Code v2.1.101 with /team-onboarding, /ultraplan, Monitor tool (#73)

* docs: sync to Claude Code v2.1.101 with new feature coverage

Bumps all English docs from v2.1.97 to v2.1.101, adds mandatory Sources
footer block (previously missing), and documents three new features
shipped between v2.1.98 and v2.1.101:

- /team-onboarding (v2.1.101) — new built-in command for generating
  teammate ramp-up guides. Added to 01-slash-commands and CATALOG.
- /ultraplan (v2.1.91+, cloud-env auto-creation in v2.1.101) — full
  section in 09-advanced-features covering launch methods, status
  indicators, and execution options. Replaces prior 3-line stub.
- Monitor tool (v2.1.98) — full section in 09-advanced-features with
  stream-filter and poll-emit patterns and the grep --line-buffered
  warning. Added to resources.md feature table.

Vietnamese and Chinese translations are not touched in this sync.

* fix(docs): address review feedback on v2.1.101 sync

- Correct /team-onboarding availability date (April 10 → April 11, 2026)
- Fix uninitialized \$last variable in Monitor poll-and-emit example
- Update CATALOG.md New Features heading to April 2026 and add Monitor
  Tool, /team-onboarding, and Ultraplan auto-create entries

CATALOG.md

@@ -7,7 +7,7 @@
 
 > Quick reference guide to all Claude Code features: commands, agents, skills, plugins, and hooks.
 
-**Navigation**: [Commands](#slash-commands) | [Permission Modes](#permission-modes) | [Subagents](#subagents) | [Skills](#skills) | [Plugins](#plugins) | [MCP Servers](#mcp-servers) | [Hooks](#hooks) | [Memory](#memory-files) | [New Features](#new-features-march-2026)
+**Navigation**: [Commands](#slash-commands) | [Permission Modes](#permission-modes) | [Subagents](#subagents) | [Skills](#skills) | [Plugins](#plugins) | [MCP Servers](#mcp-servers) | [Hooks](#hooks) | [Memory](#memory-files) | [New Features](#new-features-april-2026)
 
 ---
 
@@ -85,6 +85,8 @@ Commands are user-invoked shortcuts that execute specific actions.
 | `/fast` | Toggle fast output mode | Speed up responses |
 | `/terminal-setup` | Configure terminal integration | Setup terminal features |
 | `/upgrade` | Check for updates | Version management |
+| `/team-onboarding` | Generate a teammate ramp-up guide from this project's Claude Code usage | Onboarding new teammates (v2.1.101) |
+| `/ultraplan` | Hand a planning task to a Claude Code web session in plan mode | Heavy planning offload (Research Preview, v2.1.91+) |
 
 ### Custom Commands (Examples)
 
@@ -429,10 +431,13 @@ cp 02-memory/personal-CLAUDE.md ~/.claude/CLAUDE.md
 
 ---
 
-## New Features (March 2026)
+## New Features (April 2026)
 
 | Feature | Description | How to Use |
 |---------|-------------|------------|
+| **Monitor Tool** | Watch a background command's stdout stream and react to events instead of polling (v2.1.98+) | Use the Monitor tool via [Advanced Features](09-advanced-features/) |
+| **/team-onboarding** | Auto-generate a teammate ramp-up guide from the project's Claude Code setup (v2.1.101) | Run `/team-onboarding` in your project |
+| **Ultraplan auto-create** | Cloud environment created automatically on first `/ultraplan` invocation — no manual setup required (v2.1.101) | Use `/ultraplan <prompt>` |
 | **Remote Control** | Control Claude Code sessions remotely via API | Use the remote control API to send prompts and receive responses programmatically |
 | **Web Sessions** | Run Claude Code in a browser-based environment | Access via `claude web` or through the Anthropic Console |
 | **Desktop App** | Native desktop application for Claude Code | Use `/desktop` or download from Anthropic website |
@@ -513,5 +518,8 @@ chmod +x ~/.claude/hooks/*.sh
 
 ---
 
-**Last Updated**: April 9, 2026
-**Claude Code Version**: 2.1.97
+**Last Updated**: April 11, 2026
+**Claude Code Version**: 2.1.101
+**Sources**:
+- https://code.claude.com/docs/en/overview
+- https://code.claude.com/docs/en/commands