feat: add the-workshop plugin — multi-agent coordination with persistent desks

The Workshop puts long-running AI agents (desks) in the same room,
on the same work, each with its own memory and history, sharing one
workspace so you direct the work instead of relaying it.

Components:
- Workshop TA agent (room coordinator)
- Skills: desk-open, desk-journal, signal-write, bench-read
- Marketplace entry for one-command install

Install: copilot plugin install the-workshop@awesome-copilot

Complements Ember (partnership for one agent) with coordination
for many agents. Install both for the full stack.

Source: https://github.com/jennyf19/the-workshop

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 26faf13e-639c-4a21-ac05-c0dc2bff7c62

skills/desk-journal/SKILL.md

@@ -0,0 +1,68 @@
+---
+name: desk-journal
+description: 'Write, append, or read desk journal entries. The journal is persistent memory — what survives session boundaries. A good entry has: what was done, current state, next step.'
+---
+
+# Desk Journal
+
+Manage a desk's journal — the persistent memory that survives
+session boundaries.
+
+## When to use
+
+- **End of session:** Write what was done, current state, next step
+- **Start of session:** Read the journal to pick up where you left off
+- **Mid-session checkpoint:** Note significant progress or decisions
+- **Desk wind-down:** Write a final summary when a desk is being closed
+
+## How to write a journal entry
+
+Append to `desks/<desk-name>/journal.md`. Each entry is a section:
+
+```markdown
+## <date> — <short summary>
+- **Worked on:** <what was done this session>
+- **Current state:** <where things stand right now>
+- **Next step:** <what the next session should pick up>
+```
+
+### Guidelines
+
+- **Be specific.** "Worked on security scanning" is useless to the
+  next session. "Scanned repos A, B, C for CWE-502; found 3
+  findings in A, 0 in B and C; findings triaged to bench" — that's
+  a trail.
+- **Include what didn't work.** Dead ends are valuable — they prevent
+  the next session from walking the same path.
+- **Keep it short.** The journal is a trail marker, not a diary.
+  3-5 lines per entry. If you need more, the important context
+  should go on the bench as a separate artifact.
+- **Always include next step.** The next session starts from zero.
+  Without a next step, it has to re-derive everything.
+
+## End-of-desk entry
+
+When a desk is being wound down (not just a session ending, but
+the desk itself closing):
+
+```markdown
+## <date> — Desk closed
+- **Summary:** <what this desk accomplished overall>
+- **Artifacts:** <what's on the bench from this desk>
+- **Handoff:** <anything another desk or the operator needs to know>
+```
+
+## Reading the journal
+
+At session start, read the desk's journal to pick up context.
+The most recent entry is the most important — it has the current
+state and next step. Earlier entries provide history if needed.
+
+## Principles
+
+- The journal is a cairn — stones left so the next traveler finds
+  the way. Every entry is a stone.
+- Honesty over completeness. "I got stuck on X and don't know why"
+  is more useful than silence.
+- The journal is for the next session, not for the current one.
+  Write for someone who knows nothing about what you just did.