Promote stable workspace product for 3.0.0

Freeze the current workspace-first surface as the stable 3.0 contract and reposition the
landing docs, CLI help, and public contract around the stable workspace path after the
one-shot proof.

Bump the package and catalog compatibility to 3.0.0, add a dedicated workspace walkthrough
tape/GIF, and mark the 3.0.0 roadmap milestone done while keeping runtime capability
unchanged in this release.

Validation: uv lock; UV_CACHE_DIR=.uv-cache make check; UV_CACHE_DIR=.uv-cache make dist-check;
UV_CACHE_DIR=.uv-cache uv build; UV_CACHE_DIR=.uv-cache uvx --from twine twine check dist/*;
built-wheel CLI smoke for pyro --help and pyro workspace --help; vhs validate plus rendered
workspace-first-run.gif outside the sandbox because vhs crashes when sandboxed.

CHANGELOG.md

@@ -2,6 +2,16 @@
 
 All notable user-visible changes to `pyro-mcp` are documented here.
 
+## 3.0.0
+
+- Promoted the workspace-first product surface to stable across the CLI, Python SDK, and MCP
+  server, with `pyro run` retained as the stable one-shot entrypoint.
+- Repositioned the main docs, help text, examples, and walkthrough assets around the stable
+  workspace path: create, sync, exec or shell, services, snapshots/reset, diff/export, and
+  delete.
+- Froze the `3.x` public contract around the current workspace surface without introducing new
+  runtime capability in this release.
+
 ## 2.10.0
 
 - Replaced the workspace-level boolean network toggle with explicit workspace network policies: