Revert "feat(ecc): prune plugin 43→12 items, promote 7 rules to .claude/rules/ (#245)"

This reverts commit 1bd68ff534.

.cursor/rules/context-dev.md

@@ -0,0 +1,25 @@
+---
+description: "Development context: active coding mode with implementation-first priorities"
+alwaysApply: false
+---
+
+# Development Context
+
+Mode: Active development
+Focus: Implementation, coding, building features
+
+## Behavior
+- Write code first, explain after
+- Prefer working solutions over perfect solutions
+- Run tests after changes
+- Keep commits atomic
+
+## Priorities
+1. Get it working
+2. Get it right
+3. Get it clean
+
+## Tools to favor
+- Edit, Write for code changes
+- Bash for running tests/builds
+- Grep, Glob for finding code