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/11-collaboration-humans-and-agents/lab/issue.md

@@ -0,0 +1,25 @@
+<!--
+  Module 11 lab — the issue to file (the "contract" / station 1 of the loop).
+
+  Create a new issue on your git host. Paste the line below as the TITLE and everything under
+  "Body" as the issue description. Note the number the host assigns it (e.g. #42) — every later
+  step references it. Assign it to yourself for the first run-through.
+-->
+
+Title: Add a `clear-done` command to remove completed tasks
+
+Body:
+
+**What**
+Add a `clear-done` command to the tasks CLI that removes every task already marked done, leaving
+the pending ones untouched.
+
+**Why**
+After working through a list, the completed items pile up as noise. There's currently no way to
+clear them out short of editing `tasks.json` by hand.
+
+**Acceptance criteria**
+- `python cli.py clear-done` removes all completed tasks and keeps all pending ones.
+- It prints how many tasks were removed.
+- The removal logic lives in `tasks.py` (a `TaskList` method), not in `cli.py`.
+- Running it when nothing is done is a no-op that removes 0 tasks (no crash).