docs: add [skip ci] documentation to CONTRIBUTING.md

CONTRIBUTING.md

@@ -332,6 +332,98 @@ Ideally, the new branch should be based on the latest `dev` branch.
 1. Reviewer and contributor may have discussions back and forth until all comments addressed.
 1. Wait for the pull request to be merged.
 
+## Skipping CI
+
+MONAI's CI pipelines run automatically on every push and pull request.
+These pipelines can be resource-intensive, especially the full premerge matrix
+which spans multiple OSes, Python versions, and PyTorch versions.
+
+To reduce unnecessary resource consumption and speed up iteration, you can
+skip CI on commits that don't need automated validation — for example,
+documentation-only changes, README updates, workflow YAML changes, or WIP
+commits during development.
+
+### Mechanism
+
+GitHub Actions natively supports skipping `push` and `pull_request` workflows
+when the commit message contains any of the following strings:
+
+- `[skip ci]`
+- `[ci skip]`
+- `[no ci]`
+- `[skip actions]`
+- `[actions skip]`
+
+These are case-insensitive. `[skip ci]` is the recommended convention for
+this repository.
+
+Alternatively, you can add a `skip-checks: true` trailer at the end of the
+commit message, preceded by two blank lines:
+
+```
+commit message
+
+skip-checks: true
+```
+
+### Usage
+
+Add the keyword anywhere in the commit message when committing:
+
+```bash
+git commit -s -m 'update docs [skip ci]'
+```
+
+If the HEAD commit of a pull request contains the skip instruction,
+the entire PR's pull_request-triggered workflows are skipped.
+
+### Which workflows are affected
+
+The skip instruction applies only to workflows using `on: push` or
+`on: pull_request` events. In this repository, that includes:
+
+- **premerge** (multi-OS lint, tests, packaging, docs build)
+- **premerge-min** (minimal dependency matrix)
+- **premerge-gpu** (GPU tests)
+- **CodeQL analysis**
+- **Docker build**
+- **Release packaging**
+- **Setup/install tests**
+
+The following workflows use different event types (`issue_comment`,
+`repository_dispatch`, `schedule`, `workflow_dispatch`) and are **not**
+affected by `[skip ci]`:
+
+- **Blossom-CI** (triggered by `/build` comment — maintainers only)
+- **ChatOps** (triggered by `/black` or `/integration-test` comment)
+- **Integration tests** (triggered by `/integration-test` comment)
+- **Cron jobs** (scheduled, not per-commit)
+- **Weekly preview** (scheduled, not per-commit)
+- **Conda build** (scheduled, not per-commit)
+
+### Important caveat
+
+If a workflow is skipped via `[skip ci]`, its associated checks remain in
+"Pending" state. If your pull request requires those checks to pass before
+merging, you will need to push a new commit **without** the skip instruction
+to trigger the CI pipelines.
+
+### When to use
+
+Use `[skip ci]` for commits that are safe to skip CI:
+
+- Documentation-only changes (`docs/`, `README.md`, docstrings)
+- Workflow configuration changes (`.github/`)
+- Repository metadata (`.gitignore`, `CONTRIBUTING.md`, `LICENSE`)
+- WIP or draft commits during local development
+
+Do **not** use `[skip ci]` for commits that change:
+
+- Source code in `monai/`
+- Test files in `tests/`
+- Dependencies (`requirements*.txt`, `setup.cfg`, `setup.py`)
+- Anything that could affect correctness or compatibility
+
 ## The code reviewing process