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/repl-block/README.org

@@ -0,0 +1,28 @@
+#+TITLE: repl-block
+
+Extract a ~#+begin_src lisp~ block from an .org file and output it to stdout,
+ready to pipe to ~repl~ or inspect.
+
+== Usage
+
+#+begin_src shell
+  repl-block org/file.org --function foo | repl
+  repl-block org/file.org --block 3
+  repl-block org/file.org --function foo --package :my-package
+  repl-block org/file.org                  # list all blocks
+#+end_src
+
+== Identifying blocks
+
+By function name (--function): scans all blocks for (defun <name> ...) and
+outputs the containing block. By index (--block): 1-based position in file.
+
+The --package flag prepends an ~(in-package ...)~ form so the REPL evaluates
+in the right namespace.
+
+Combine with ~repl~ to send a block directly to the daemon:
+  repl-block org/channel-tui-view.org --function view-status --package :passepartout.channel-tui | repl
+
+== Requires
+
+Python 3. No dependencies.