docs: sync to Claude Code v2.1.126 (six new releases since April 27) (#111)

Bumps tutorial coverage from v2.1.119 → v2.1.126 (May 1, 2026 release).
v2.1.120 was rolled back on its first release day (2026-04-24) but
re-released 2026-04-28 with regressions fixed; v2.1.124/125 skipped.

New feature documentation:
- claude project purge (v2.1.126) — 10-cli
- claude plugin prune / --prune (v2.1.121) — 07-plugins, 10-cli
- claude ultrareview [target] (v2.1.120) — 10-cli
- ${CLAUDE_EFFORT} placeholder + type-to-filter /skills (v2.1.120-121) — 03-skills
- alwaysLoad MCP server config option (v2.1.121) — 05-mcp
- PostToolUse.updatedToolOutput for non-MCP tools (v2.1.121) — 06-hooks
- ANTHROPIC_BEDROCK_SERVICE_TIER, AI_AGENT env vars — 10-cli
- --dangerously-skip-permissions extended path coverage — 09-advanced-features
- Windows PowerShell-as-primary-shell + /model gateway discovery (v2.1.126)
- OAuth code paste fallback (v2.1.126) — 10-cli

Fixes:
- xhigh missing from 03-skills effort enum (regression from April 24)
- README.md latest-version claims (lines 105, 204) and version badge
- CHANGELOG.md v2.4.0 stale "v2.1.120 was rolled back" paragraph

Footer refresh: 22 in-scope English files bumped to May 2, 2026 / 2.1.126.
Localized vi/zh/uk/ja trees out of scope (community-maintained).

09-advanced-features/README.md

@@ -807,6 +807,10 @@ Permission modes control what actions Claude can take without explicit approval.
 
 Cycle through modes with `Shift+Tab` in the CLI. Set a default with the `--permission-mode` flag or the `permissions.defaultMode` setting.
 
+> **`--dangerously-skip-permissions` extended path coverage (v2.1.121, v2.1.126)**: The `--dangerously-skip-permissions` CLI flag (and equivalent `bypassPermissions` mode) now bypasses prompts for writes to a much broader allowlist — `.claude/skills/`, `.claude/agents/`, `.claude/commands/`, `.claude/`, `.git/`, `.vscode/`, and shell config files. Catastrophic removal commands (`rm -rf /`, etc.) still prompt regardless of mode. Treat the flag as a sharper tool than before; use it only in throwaway sandboxes.
+
+> **Windows shell detection (v2.1.120, v2.1.126)**: Git for Windows / Git Bash is no longer required. When Git Bash is absent, Claude Code uses PowerShell as the shell tool. From v2.1.126 PowerShell is the *primary* shell when the PowerShell tool is enabled, and detection covers PowerShell 7 installed via the Microsoft Store, MSI without PATH, or as a `.NET global tool`.
+
 ### Activation Methods
 
 **Keyboard shortcut**:
@@ -2162,8 +2166,8 @@ For more information about Claude Code and related features:
 
 ---
 
-**Last Updated**: April 24, 2026
-**Claude Code Version**: 2.1.119
+**Last Updated**: May 2, 2026
+**Claude Code Version**: 2.1.126
 **Sources**:
 - https://code.claude.com/docs/en/permission-modes
 - https://code.claude.com/docs/en/interactive-mode