feat(hub-guide): expand plugin with 26 best-practice skills, hooks, and references

Transform hub-guide from a single-skill Hub monorepo guide into a
comprehensive programming best-practice plugin covering all situations.

Skills (26):
- Core: engineering-principles, clean-code, clean-architecture,
  design-patterns, testing, error-handling, security, api-design,
  git-workflow, documentation, logging-observability, performance
- Languages: typescript, python, rust, go
- Frameworks: react-frontend, elysiajs, hono-backend, drizzle-database, nextjs
- Infrastructure: docker, ci-cd, monitoring
- Monorepo: monorepo, hub-guide (existing)

Hooks:
- SessionStart: auto-detect project type and activate relevant skills
- PreToolUse (Write|Edit): inject language-specific rules per file type

Reference files for deep dives:
- clean-architecture/references/solid.md (SOLID + component principles)
- design-patterns/references/catalog.md (full GoF catalog with examples)
- testing/references/mocks.md (test double taxonomy)

Restructure plugin to modern skills/ directory format.

hooks/scripts/detect-file-type.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+# hub-guide: detect file extension from tool input and suggest language-specific rules
+# Runs before Write/Edit to inject best-practice context
+
+TOOL_INPUT="$1"
+
+# Extract file path from tool input (looks for "file_path" in JSON)
+FILE_PATH=$(echo "$TOOL_INPUT" | grep -o '"file_path"[[:space:]]*:[[:space:]]*"[^"]*"' | head -1 | sed 's/.*"file_path"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/')
+EXT="${FILE_PATH##*.}"
+
+case "$EXT" in
+  ts|tsx)
+    echo "📐 [hub-guide] TypeScript file — apply typescript skill rules (strict types, no-any, proper generics)"
+    ;;
+  py)
+    echo "📐 [hub-guide] Python file — apply python skill rules (type hints, PEP 8, no wildcard imports)"
+    ;;
+  rs)
+    echo "📐 [hub-guide] Rust file — apply rust skill rules (ownership, error handling, clippy clean)"
+    ;;
+  go)
+    echo "📐 [hub-guide] Go file — apply go skill rules (idiomatic Go, interfaces, error handling)"
+    ;;
+  js|jsx)
+    echo "📐 [hub-guide] JavaScript file — apply typescript skill rules (ESM, modern JS)"
+    ;;
+  dockerfile|Dockerfile)
+    echo "📐 [hub-guide] Dockerfile — apply docker skill rules (multi-stage, minimal layers, no root)"
+    ;;
+  yml|yaml)
+    echo "📐 [hub-guide] YAML file — check ci-cd and docker skill rules"
+    ;;
+esac