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/02-version-control-as-a-safety-net/lab/gitignore-starter

@@ -3,10 +3,10 @@
 # A .gitignore tells Git which files to leave untracked. The rule of thumb: version the things a
 # human (or AI) authors, ignore the things a machine generates. For our tasks-app:
 
-# Runtime state — generated by running the app, not authored. Not something you want in history.
+# Runtime state, generated by running the app, not authored. Not something you want in history.
 tasks.json
 
-# Python bytecode caches — generated, never edited by hand.
+# Python bytecode caches: generated, never edited by hand.
 __pycache__/
 *.pyc