docs: sync to Claude Code v2.1.278 (#183)

* docs: sync to Claude Code v2.1.278

Type: docs

Audit of the tutorial against Claude Code 2.1.278 (repo baseline was
2.1.263). Fixes claims the repo asserts that are now false; new-feature
coverage is English-only.

P0 - the repo stated the opposite of current behavior:
- AGENTS.md: the claude-md skill said Claude Code "does not read
  AGENTS.md directly" in all 5 languages. It has since v2.1.277, when no
  CLAUDE.md exists at or above the working directory.
- /output-style: listed as "Removed in v2.1.91" in 5 languages and in
  09-advanced-features. Re-added in v2.1.269; row moved out of the
  Deprecated Commands table.
- Permission rules: setup-auto-mode-permissions.py seeded Write(*),
  Glob(*) and NotebookEdit(*), which Claude Code accepts but never
  consults and warns about at startup. Removed; same fix in the
  config-examples.json profile and the 06/09 category tables.
- taskOutputMaxChars: documented as live. The TaskOutput tool was
  removed in v2.1.278 and the key is inert.

P1:
- Dynamic workflow "medium" guideline is fewer than 10 agents, not 15;
  the default is small on Pro plans since v2.1.271.
- Todo-tool availability restated as the official allowlist (Claude 3.x,
  Opus 4-4.7, Sonnet 4-4.6, Haiku 4.5) instead of a denylist; 23 sites
  across 5 languages.
- Memory hierarchy now notes the AGENTS.md fallback.
- Auto-mode classifier cost qualified: not charged on Enterprise plans
  and Claude API accounts since v2.1.278.

P3 (English only): full AGENTS.md section in 02-memory; omitClaudeMd
subagent field; plugin eval / --json / --accept-command / --marketplace;
maxEffortLevel, bashEditDiffEnabled, syncClaudeAi*, 4 env vars,
--system-prompt-snapshot, --plugin-dir folders; send-now key and Monitor
deadlines; checkpoints subagent-edit limitation.

Learning skills audited clean: 100 quiz questions and 100 Review
pointers all valid, 20 self-assessment options correctly mapped.

Cross-file anchors: 15 broken before, 15 after, 0 introduced.

* docs: address review — stale version stamps, /output-style re-add, permission tables

04-subagents/README.md

@@ -144,6 +144,7 @@ to solving problems.
 | `initialPrompt` | No | Auto-submitted first turn when the subagent runs as the main agent |
 | `color` | No | Display color for the subagent in the task list and transcript. Accepts `red`, `blue`, `green`, `yellow`, `purple`, `orange`, `pink`, or `cyan` |
 | `experimental` | No | Experimental settings block (v2.1.248+). `experimental.cacheTtl` sets the cache TTL for this subagent — `"5m"` or `"1h"` |
+| `omitClaudeMd` | No | Set to `true` to launch the subagent without the user, project, and local CLAUDE.md files (v2.1.271+). Managed policy files still load, except for managed subagents. Ignored when the agent runs as the main session agent via `--agent` or the `agent` setting. Also accepted in `--agents` JSON |
 
 #### Subagent Model Environment Variables
 
@@ -1331,8 +1332,8 @@ See the OpenTelemetry section in [Advanced Features → Telemetry](../09-advance
 
 ---
 
-**Last Updated**: September 6, 2026
-**Claude Code Version**: 2.1.263
+**Last Updated**: September 19, 2026
+**Claude Code Version**: 2.1.278
 **Sources**:
 - https://code.claude.com/docs/en/sub-agents
 - https://github.com/anthropics/claude-code/blob/main/CHANGELOG.md