Add workflow_dispatch to propagate wrapper; add update-synced-workflows workflow

[Copilot]

The propagate wrapper installed by Bootstrap only fired on push, with no way to trigger it manually. There was also no mechanism to roll out wrapper template changes to already-bootstrapped repositories.

Changes

bootstrap-copilot-sync.sh

• Updated propagate_b64 to include workflow_dispatch: in the installed propagate-copilot-instructions.yml wrapper

on:
  push:
    branches: ["main"]
    paths: [...]
  workflow_dispatch:   # ← added

New: update-synced-workflows.yml + update-synced-workflows.sh

• workflow_dispatch-only workflow for propagating wrapper template updates to all Cratis repos
• Skips repos where both wrapper files already match the current blob SHAs (idempotent)
• Skips repos where neither wrapper is present (not yet bootstrapped — run bootstrap first)
• For repos that need updating: creates blobs → tree → commit → update-synced-workflows branch (via GraphQL) → opens a PR
• Same GraphQL-first, REST-fallback PR creation strategy as Bootstrap

README.md

• Updated the getting-started propagate snippet to reflect workflow_dispatch and the full paths list
• Added documentation for update-synced-workflows.yml

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