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).

05-mcp/README.md

@@ -207,6 +207,27 @@ When MCP tool descriptions exceed 10% of the context window, Claude Code automat
 
 > **Note:** Tool search requires Sonnet 4 or later, or Opus 4 or later. Haiku models are not supported for tool search.
 
+### Bypassing Tool Search per Server (v2.1.121+)
+
+If a particular MCP server's tools are needed on every turn, mark its
+configuration with `"alwaysLoad": true` to skip tool-search deferral and
+keep its tools always available:
+
+```json
+{
+  "mcpServers": {
+    "always-on-tool": {
+      "command": "node",
+      "args": ["./tools/always.js"],
+      "alwaysLoad": true
+    }
+  }
+}
+```
+
+Use sparingly — every always-loaded tool consumes context that could
+otherwise be used for tool search to surface a more relevant tool.
+
 ## Dynamic Tool Updates
 
 Claude Code supports MCP `list_changed` notifications. When an MCP server dynamically adds, removes, or modifies its available tools, Claude Code receives the update and adjusts its tool list automatically -- no reconnection or restart required.
@@ -1111,8 +1132,8 @@ export GITHUB_TOKEN="your_token"
 
 ---
 
-**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/mcp
 - https://code.claude.com/docs/en/changelog