tools: add repl-block, check-tangle; move existing tools into memex

New tools (projects/<tool>/ — standalone, git-committed):
- repl-block: extract and pipe lisp blocks from org files to the REPL
- check-tangle: tangle + compile in one step, reports errors

Existing tools moved from ~/.opencode/bin/ into memex (survives reinstalls):
- repl, tangle, org-eval, verify-repl

AGENTS.md updated:
- Tool reference table with all 7 tools
- Package reference table for passepartout and cl-tty
- Updated tangle command to use project-local tools

.opencode/commands/ added: check-parens, repl-block, check-tangle commands

.opencode/commands/check-parens.md

@@ -0,0 +1,8 @@
+---
+description: Check paren balance in lisp blocks of .org files
+---
+
+Run `projects/check-parens/check-parens` on the given .org files to verify all
+`#+begin_src lisp` blocks have balanced parentheses.
+
+Usage: /check-parens <file.org> [<file.org> ...]