feat(course): build out all 27 modules, capstone, scaffold, and conventions

Scaffold the course repo and author the full curriculum in dependency-chain
order, following the settled build decisions in handoff.md.

- Scaffold: course README, vendor-neutral AGENTS.md (dogfoods Module 5),
  _TEMPLATE.md (the fixed 9-section module shape), root .gitignore, ship config.
- Modules 1-2: reference exemplars (locked for tone/depth/lab style).
- Modules 3-27: full lessons + runnable labs, each following the template,
  respecting the chain, vendor/model-agnostic, with "feel the pain" labs.
- Module 8 hosting comparison web-researched and date-stamped (as of 2026-06-22),
  not written from memory; expansion-zone modules carry Verify-before-publish.
- Capstone: the full loop end to end on the running tasks-app example.

Lab code syntax-checked (Python/shell/YAML); every module has the 7 core
template sections.

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

modules/07-worktrees-running-agents-in-parallel/lab/agent-b-prompt.md

@@ -0,0 +1,14 @@
+# Agent B prompt — the `count` command
+
+Paste this into the AI session you've pointed at the `tasks-app-count` worktree folder.
+
+---
+
+Add a `count` command to this task app that prints how many tasks are still pending.
+
+- Reuse the existing `pending()` method on `TaskList` in `tasks.py`; don't reimplement it.
+- Wire a `count` command into the dispatch in `cli.py`.
+- Running `python cli.py count` should print something like `2 pending` (the number of tasks not
+  marked done).
+
+Make the change, then stop — I'll review the diff and commit it myself.