Build out all 27 modules + capstone (#1)

Co-authored-by: claude <claude@jpaul.io>
Co-committed-by: claude <claude@jpaul.io>

modules/11-collaboration-humans-and-agents/lab/pr-body.md

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+<!--
+  Module 11 lab — the pull request description (station 4 of the loop).
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+  Paste this as the body when you open the PR from your branch into main. The "Closes" line is the
+  load-bearing part: replace 42 with YOUR issue number. On merge to the default branch, the host
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+
+## What this does
+
+Adds a `clear-done` command that removes all completed tasks. The removal logic is a new `TaskList`
+method in `tasks.py`; `cli.py` just wires up the command and reports how many tasks were removed.
+
+## How I tested it
+
+- Added a mix of pending and done tasks, ran `clear-done`, confirmed only the done ones were removed
+  and the count printed.
+- Ran `clear-done` with nothing marked done — removed 0, no crash.
+
+## Review notes
+
+Small two-file change. Check that the logic sits in `tasks.py` (not the CLI) and that the empty /
+nothing-done case is handled.
+
+Closes #42