fix repl-block, check-tangle, commands: READMEs, exit codes, path resolution

repl-block:
- Listing mode exits 0, not 1 (listing is not an error)
- Dead lines parameter removed from find_by_function
- Block listing goes to stderr (not stdout) so piped use works
- Added README.org

check-tangle:
- Fixed tangle tool resolution: prefer local projects/tangle-tool/tangle
- Fixed path resolution for relative and absolute tangle paths
- Removed 2>/dev/null suppression so tangle errors are visible
- Added README.org

Commands:
- Rewrote all three .opencode/commands/*.md with proper prompts

projects/check-tangle/README.org

@@ -0,0 +1,22 @@
+#+TITLE: check-tangle
+
+Tangle an .org file and compile the resulting .lisp with SBCL in one step.
+
+== Usage
+
+#+begin_src shell
+  check-tangle org/file.org
+#+end_src
+
+Exit 0 if compilation succeeds, 1 if tangling or compilation fails.
+
+== What it checks
+
+1. Reads the ~:tangle~ header from the org file to find the target .lisp path
+2. Runs ~tangle~ to generate the .lisp from the .org source
+3. Runs ~sbcl compile-file~ on the result
+4. Reports the first compile error if any
+
+== Requires
+
+Emacs (for tangling), SBCL (for compilation).