style(no-slop): remove every em-dash + banned words across all modules + capstone

Apply the no-ai-slop standard (now binding in AGENTS.md): the em-dash character is
banned outright (restructured, not blind-replaced), plus the banned word/phrase
list (delve, leverage, robust, seamless, truly, unlock, etc.). 0 em-dashes remain
in modules + capstone; the only "robust" left is the planted M10 ai-change.patch
trap. Module H1 titles use a colon separator.

All deliberate teaching devices preserved; labs compile/parse (py/sh/yaml/json);
no junk. AGENTS.md updated with the hard no-slop rules.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TfzV5QvtPDz8LJS3Pu5VLT

modules/13-testing-in-the-ai-era/lab/tasks-app/README.md

@@ -1,16 +1,16 @@
-# Demo app — `tasks` (Module 13 copy)
+# Demo app: `tasks` (Module 13 copy)
 
 The same tiny task tracker from Modules 1 and 2, with one feature added: a `count` command backed
 by `TaskList.pending_count()`. Use this copy for the Module 13 lab so everyone starts from the same
-code — including the same latent bug.
+code, including the same latent bug.
 
 If you already have a `tasks-app` from earlier modules, you can use that instead; just make sure it
 has a `count` command (the Module 2 lab added one). The planted bug in this copy is there on purpose.
 
 ## Files
 
-- `tasks.py` — core logic (`Task`, `TaskList`), now with `pending_count()`.
-- `cli.py` — command-line front end. Adds `count`.
+- `tasks.py`: core logic (`Task`, `TaskList`), now with `pending_count()`.
+- `cli.py`: command-line front end. Adds `count`.
 
 ## Run it
 
@@ -22,4 +22,4 @@ python cli.py list
 python cli.py count
 ```
 
-Requires Python 3.10+. No third-party packages — tests use the standard library `unittest`.
+Requires Python 3.10+. No third-party packages; tests use the standard library `unittest`.