Sync GHCP-hardened dashboard, signal-write, and workshop-ta from awesome-copilot

[jennyf19]

Brings the-workshop source to full parity with the reviewed/published versions on awesome-copilot PR #2343, which cleared all GitHub Copilot review comments (10 fixed, 1 parked-with-rationale).

Files synced (byte-identical to the published versions)

.github/extensions/signals-dashboard/extension.mjs

• Serialize stash read-modify-write behind a per-desk mutex (no lost updates).
• Order signals by explicit ISO timestamp (clone-safe) instead of filesystem mtime.
• Keep desks whose latest signal is malformed as "awaiting" instead of dropping them.
• Gate the calibration badge on a real gap value (no false green when gap is null).
• prefers-reduced-motion CSS; toast aria-live region (a11y).
• Rename canvas action open_desk → get_desk_path (it only returns a path).
• Handle server.listen errors (no unhandled rejection on bind failure).

skills/signal-write/SKILL.md

• Document timestamp + run_id, signal ordering guidance, and the outcome (calibration) signal schema.

agents/workshop-ta.md

• Persistent-workstream framing (a desk is a seat sessions pick up, not one long-running process).
• Self-contained Cairn disposition; canvas made optional; desks/_ta/ partnership-signal storage.
• "The Forge" → "Autonomous Desks".

Notes

• No Blazor/source changes — docs, canvas, skill, and agent only.
• Establishes parity so awesome-copilot and source no longer drift after the GHCP review round.

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com