feat(labs): make every lab a self-contained, skip-friendly starting point

Each lab now stands on its own; no hard dependency on prior labs.
- App-based labs get a canonical tasks-app snapshot in lab/start/ (three
  baselines: v0 add/list/done; v1 +count; v2 +count/delete), assigned by where
  each module sits in the command timeline. Modules with a purpose-built app
  (M10 trap, M13 planted bug, M21) snapshot their own app; planted devices kept.
- Self-contained labs (M15/17/18/19/22/23/24/25/27, which operate on their own
  lab files) get a preamble pointing at modules/NN/lab/.
- Every module + capstone gets a "Starting point (skip-friendly)" preamble:
  copy the snapshot, git init -b main, commit -> clean status, then start.

Lets a learner skip around or recover: copy start/, commit, go. All snapshots
run; tools/check.sh passes; no em-dashes.

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

modules/14-continuous-integration/lab/start/README.md

@@ -0,0 +1,25 @@
+# Demo app: `tasks`
+
+A deliberately tiny command-line task tracker. It exists to be *changed by an AI*, so it's small
+enough to read in a minute but real enough to have more than one file, which is exactly where the
+copy-paste workflow starts to hurt.
+
+This is the running example for **Module 1** (where you feel the copy-paste problem) and **Module 2**
+(where you put it under version control).
+
+## Files
+
+- `tasks.py`: the core logic (`Task`, `TaskList`).
+- `cli.py`: the command-line front end. Reads/writes `tasks.json`.
+
+## Run it
+
+```bash
+python cli.py add "read module 1"
+python cli.py add "set up my editor"
+python cli.py list
+python cli.py done 0
+python cli.py list
+```
+
+Requires Python 3.10+ (it uses `list[Task]` style type hints). No third-party packages.