docs: sync to Claude Code v2.1.235 (#174)

* docs: sync to Claude Code v2.1.235

Syncs the tutorial repo from v2.1.233 to v2.1.235, fixes a fabricated
plugin-command reference and a wrong lesson-quiz answer, closes translation
fan-out gaps, and documents six new features from v2.1.234/v2.1.235.

* docs(slash-commands): scope v2.1.234 dialog-command claims to the fullscreen TUI

The v2.1.234 changelog carries two separate entries: /permissions opening
mid-turn unconditionally, and the /add-dir, /autocompact, /theme, /help,
/config and /advisor dialogs opening mid-turn in the fullscreen TUI. The
sync flattened both into one unqualified bullet, so a reader on the default
renderer would find the described behavior absent.

Also corrects the CATALOG usage-limit auto-continue row, which described an
on-by-default feature as opt-in ("Enable via /config"); the changelog says
"turn it off in /config".

* docs(advanced-features): correct spellcheck value shape, default, and scope

settings.md documents `spellcheck` as object-valued
(`{"enabled": true, "language": "en_GB"}`) and read from user settings, the
--settings flag, and managed settings only; interactive-mode.md adds that it
is off by default and needs aspell, hunspell, or ispell on PATH. CATALOG told
readers to set a bare `"spellcheck": true`, and both settings tables sit under
preambles promising project-scope settings work, which for this key they do
not.

Also repoints CATALOG's hook-configuration example at pre-tool-check.sh; the
table rename left the example on validate-bash.py, which is not in 06-hooks/.

* docs(plugins): drop the unsupported claim that /plugin update does not exist

The sync asserted "Updating is CLI-only — there is no `/plugin update` slash
command". The plugins reference contradicts that: it refers to running
`/plugin update` twice in present tense (the cache-key section, and the
explicit-version row that says `/plugin update` reports "already at the
latest version"). The v2.1.235 binary carries no `/plugin update` string and
its own update notices point at `claude plugin update <name>` in a terminal,
so the sources conflict and neither absolute is safe to teach.

Recommends the CLI form on its documented merits instead of asserting a
negative. Mirrored to vi/ja/zh/uk and to the lesson-quiz Q8 explanation,
which taught the same false negative. Q8's correct answer is unchanged.

* docs(advanced-features): complete the v2.1.234 env-var fan-out and 04 TOC (#175)

The env-var block was still headed (v2.1.221-v2.1.233) and omitted both
variables v2.1.234 added: CLAUDE_CODE_PROJECT_DIR_NAME, which had reached
only 10-cli and CATALOG, and CLAUDE_CODE_GOAL_CHECKIN_MINUTES, which was in
prose and a CATALOG row but no env-var table.

Also adds the one missing 04-subagents TOC entry: Additional Resources was
the only H2 without one, leaving the reconciled TOC at 26 of 27 sections.

INDEX.md

@@ -13,7 +13,7 @@ This document provides a complete index of all example files organized by featur
 - **Categories**: 10 feature categories
 - **Plugins**: 3 complete plugins
 - **Skills**: 6 complete skills
-- **Hooks**: 8 example hooks
+- **Hooks**: 11 example hooks
 - **Ready to Use**: All examples
 
 ---
@@ -888,8 +888,8 @@ Want to add more examples? Follow the structure:
 
 ---
 
-**Last Updated**: August 15, 2026
-**Claude Code Version**: 2.1.233
+**Last Updated**: August 19, 2026
+**Claude Code Version**: 2.1.235
 **Sources**:
 - https://code.claude.com/docs/en/overview
 - https://code.claude.com/docs/en/hooks