docs: add internal release process docs

Author: somanshreddy

README.md

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+# HeyGen CLI
+
+A Go CLI wrapping HeyGen's v3 API. Auto-generated from our OpenAPI spec. Single
+binary, JSON-first output.
+
+## Install
+
+### Internal dev build (recommended for internal users)
+
+If `gh` is installed and authenticated:
+
+```bash
+gh api repos/heygen-com/heygen-cli/contents/scripts/install.sh \
+  --jq '.content' | base64 -d | bash
+```
+
+If you want to use a token directly:
+
+```bash
+curl -fsSL \
+  -H "Authorization: Bearer $GITHUB_TOKEN" \
+  -H "Accept: application/vnd.github.raw" \
+  https://api.github.com/repos/heygen-com/heygen-cli/contents/scripts/install.sh \
+  | bash
+```
+
+This installs the latest internal dev build from the rolling `dev` prerelease
+into `~/.local/bin` by default.
+
+### From source (contributors)
+
+Requires Go 1.23+.
+
+```bash
+git clone git@github.com:heygen-com/heygen-cli.git
+cd heygen-cli
+make install
+```
+
+This installs `heygen` to your `$GOPATH/bin` (typically `~/go/bin`).
+
+### Manual release download
+
+Download the binary for your platform from
+[Releases](https://github.com/heygen-com/heygen-cli/releases) and put it in
+your `PATH`.
+
+For this internal repository, users still need GitHub read access to download
+release assets. See [RELEASE.md](./RELEASE.md) for the maintainer release
+process and internal dev-release workflow.
+
+## Setup
+
+Authenticate with your HeyGen API key:
+
+```bash
+heygen auth login
+
+# Or non-interactively
+echo "$HEYGEN_API_KEY" | heygen auth login
+```
+
+The key is stored in `~/.heygen/credentials`. You can also use the
+`HEYGEN_API_KEY` environment variable (takes precedence over the stored key).
+
+## Usage
+
+```bash
+heygen video list --limit 10
+heygen video get <video-id>
+heygen video create --avatar-id josh_lite --script "Hello world" --voice-id en_male
+heygen avatar list
+heygen voice list --type public
+heygen video list --limit 10 --human
+```
+
+Every command supports `--help`:
+
+```bash
+heygen --help                      # show all groups
+heygen video --help                # show video commands
+heygen video-agent --help          # show flattened nested task help
+heygen webhook --help              # show flattened endpoint/event help
+```
+
+### Complex request bodies
+
+For endpoints with complex input (nested objects, unions), use `-d` to pass raw
+JSON:
+
+```bash
+heygen video-translate create -d '{"video": {"type": "url", "url": "https://..."}, "output_languages": ["es"]}'
+
+# Or from a file
+heygen video-translate create -d request.json
+
+# Or from stdin
+cat request.json | heygen video-translate create -d -
+```
+
+Flags and `-d` can be combined. Flags override fields in the JSON body.
+
+## Output modes
+
+The CLI defaults to JSON output, which is the best mode for scripts and agents:
+
+```bash
+heygen video get <video-id>
+```
+
+For human-readable tables and key/value views, add `--human`:
+
+```bash
+heygen video list --limit 10 --human
+heygen webhook --help
+```
+
+## Build & Test
+
+```bash
+make build    # build to bin/heygen
+make install  # install to $GOPATH/bin/heygen
+make test     # run all tests (mocked, no API key needed)
+make lint     # golangci-lint
+make clean    # remove build artifacts
+```
+
+## Regenerate commands from OpenAPI spec
+
+```bash
+make generate SPEC=/path/to/external-api.json
+```
+
+This reads the OpenAPI spec, generates command definitions in `gen/`, and
+formats the output. Generated files should be committed.

RELEASE.md

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+# Release Process
+
+## Install the CLI
+
+### Internal dev build
+
+Recommended for internal users who do not want to build from source.
+
+If `gh` is installed and authenticated:
+
+```bash
+gh api repos/heygen-com/heygen-cli/contents/scripts/install.sh \
+  --jq '.content' | base64 -d | bash
+```
+
+If you want to use a token directly:
+
+```bash
+curl -fsSL \
+  -H "Authorization: Bearer $GITHUB_TOKEN" \
+  -H "Accept: application/vnd.github.raw" \
+  https://api.github.com/repos/heygen-com/heygen-cli/contents/scripts/install.sh \
+  | bash
+```
+
+The installer downloads the latest internal dev build from the rolling `dev`
+prerelease and installs `heygen` into `~/.local/bin` by default.
+
+### Manual download
+
+1. Open the repo's Releases page.
+2. Find the `Internal Dev Build` prerelease.
+3. Download the archive for your platform.
+4. Extract the archive and move `heygen` into your `PATH`.
+
+### From source
+
+For contributors with Go installed:
+
+```bash
+git clone git@github.com:heygen-com/heygen-cli.git
+cd heygen-cli
+make install
+```
+
+## Release Types
+
+### Dev builds
+
+- Rolling prerelease tagged `dev`
+- Built from `main`
+- Version format: `dev-<sha>`
+- Intended for internal users and fast feedback
+
+### Stable releases
+
+- Immutable tagged releases like `v0.1.0`
+- Built from a tagged commit via GoReleaser
+- Intended for milestone cuts and broader distribution later
+
+## How to Cut a Dev Release
+
+1. Make sure `main` is in a good state.
+2. Trigger the GitHub Actions workflow:
+
+```bash
+gh workflow run dev-release.yml
+```
+
+3. Wait for the workflow to finish.
+4. Verify the `Internal Dev Build` prerelease was updated with the latest commit
+   SHA.
+5. Share the installer command or release link with internal users as needed.
+
+## How to Cut a Stable Release
+
+1. Make sure `main` is ready for a stable cut.
+2. Tag and push:
+
+```bash
+git tag v0.1.0
+git push --tags
+```
+
+3. The tag-based release workflow publishes the stable release artifacts.
+
+## Version Scheme
+
+- `dev-<sha>` for rolling internal builds
+- `v0.x.y` for pre-1.0 stable releases
+- `v1.x.y` and beyond once the CLI surface is considered stable