docs: sync to Claude Code v2.1.156 and Claude Opus 4.8 (#129)

* docs: sync to Claude Code v2.1.156 and Claude Opus 4.8

Model bump Opus 4.7 -> Opus 4.8 and version sync v2.1.150 -> v2.1.156.

- Rewrite effort-ladder claims for Opus 4.8 (default `high`; `xhigh` on
  4.8/4.7; `max` on 4.8/4.7/4.6 and Sonnet 4.6; Haiku has no effort).
- Replace soon-removed CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE with the
  `/model claude-opus-4-6[1m]` + `/fast on` path; note Opus 4.8 fast mode.
- Bump lineup tables to Opus 4.8; fix Haiku 4.5 context (1M -> 200K).
- Sweep Compatible Models + version/date footers to 2.1.156 / May 29, 2026
  across 23 English docs (incl. 2.1.138/2.1.145 stragglers).
- Re-document `/simplify` as a distinct cleanup-only command (v2.1.154).
- Add Dynamic Workflows + `/workflows`, MessageDisplay hook (count 29->30),
  disallowed-tools frontmatter, `/reload-skills` + SessionStart outputs,
  `/model` default-save inversion, lean system prompt, status-line
  COLUMNS/LINES, and the ultracode `/effort` note.

* docs(cli): drop unverified fast-mode dollar pricing, keep verified rate/speed multipliers

04-subagents/README.md

@@ -1238,8 +1238,8 @@ See the OpenTelemetry section in [Advanced Features → Telemetry](../09-advance
 
 ---
 
-**Last Updated**: May 25, 2026
-**Claude Code Version**: 2.1.150
+**Last Updated**: May 29, 2026
+**Claude Code Version**: 2.1.156
 **Sources**:
 - https://code.claude.com/docs/en/sub-agents
 - https://code.claude.com/docs/en/agent-teams
@@ -1248,4 +1248,4 @@ See the OpenTelemetry section in [Advanced Features → Telemetry](../09-advance
 - https://github.com/anthropics/claude-code/releases/tag/v2.1.138
 - https://github.com/anthropics/claude-code/releases/tag/v2.1.139
 - https://github.com/anthropics/claude-code/releases/tag/v2.1.140
-**Compatible Models**: Claude Sonnet 4.6, Claude Opus 4.7, Claude Haiku 4.5
+**Compatible Models**: Claude Sonnet 4.6, Claude Opus 4.8, Claude Haiku 4.5