chore: prepare 0.2 code freeze (NVIDIA#103)

#### Overview

Prepare the NeMo Flow `0.2.0` code freeze by cutting the release branch and moving `main` forward for post-freeze development.

- [x] I confirm this contribution is my own work, or I have the right to submit it under this project's license.
- [x] I searched existing issues and open pull requests, and this does not duplicate existing work.

#### Details

- Created upstream release branch `release/0.2` from `upstream/main` at `47e3414`, where the workspace version is `0.2.0`.
- Added `release/0.2` to `.github/nightly-alpha-branches.yaml` so nightly alpha tags continue for the frozen release branch.
- Ran `just set-version 0.3.0` to bump `main` package metadata and refreshed `Cargo.lock` with `cargo check --workspace`.
- Release-bound PRs for `0.2.0` should now target `release/0.2`; ongoing development PRs continue to target `main`.

Validation:

- `cargo check --workspace`
- `just set-version 0.3.0`
- `uv run python -c 'import yaml; [yaml.safe_load(open(path, encoding="utf-8")) for path in (".github/nightly-alpha-branches.yaml", ".github/workflows/nightly-alpha-tag.yaml")]'`
- `git diff --check`
- `uv run pre-commit run --files .github/nightly-alpha-branches.yaml Cargo.toml Cargo.lock crates/node/package.json integrations/openclaw/package.json package-lock.json`

Note: the Ruby YAML validation command from the freeze checklist could not be run locally because `ruby` is not installed; the Python YAML parse above covered the same files, and pre-commit `check yaml` passed.

#### Where should the reviewer start?

Start with `.github/nightly-alpha-branches.yaml` to confirm the release branch is included, then `Cargo.toml` for the `main` version bump to `0.3.0`.

#### Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

- Relates to: none



## Summary by CodeRabbit

* **Chores**
  * Version updated to 0.3.0 across workspace and package manifests.
  * Added release/0.2 branch to nightly build configuration.



[![Review Change Stack](https://storage.googleapis.com/coderabbit_public_assets/review-stack-in-coderabbit-ui.svg)](https://app.coderabbit.ai/change-stack/NVIDIA/NeMo-Flow/pull/103)

Authors:
  - David Gardner (https://github.com/dagardner-nv)

Approvers:
  - https://github.com/Salonijain27
  - Will Killian (https://github.com/willkill07)

URL: NVIDIA#103

Author: dagardner-nv

.github/nightly-alpha-branches.yaml

@@ -3,3 +3,4 @@
 
 branches:
   - main
+  - release/0.2

Cargo.lock

@@ -16,16 +16,16 @@ exclude = [".tmp", ".uv-cache"]
 resolver = "2"
 
 [workspace.package]
-version = "0.2.0"
+version = "0.3.0"
 edition = "2024"
 license = "Apache-2.0"
 repository = "https://github.com/NVIDIA/NeMo-Flow"
 
 [workspace.dependencies]
-nemo-flow = { version = "0.2.0", path = "crates/core", default-features = false }
-nemo-flow-adaptive = { version = "0.2.0", path = "crates/adaptive" }
-nemo-flow-ffi = { version = "0.2.0", path = "crates/ffi" }
-nemo-flow-cli = { version = "0.2.0", path = "crates/cli" }
+nemo-flow = { version = "0.3.0", path = "crates/core", default-features = false }
+nemo-flow-adaptive = { version = "0.3.0", path = "crates/adaptive" }
+nemo-flow-ffi = { version = "0.3.0", path = "crates/ffi" }
+nemo-flow-cli = { version = "0.3.0", path = "crates/cli" }
 uuid = "=1.18.1"
 
 [workspace.lints.rust]

Cargo.toml

@@ -1,6 +1,6 @@
 {
   "name": "nemo-flow-node",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "description": "Node.js bindings for the NeMo Flow agent runtime.",
   "keywords": [
     "agents",

crates/node/package.json

@@ -1,6 +1,6 @@
 {
   "name": "nemo-flow-openclaw",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "description": "NeMo Flow-authored observability plugin for OpenClaw.",
   "type": "module",
   "main": "./dist/index.js",