Adding context option to command line

[russellseymour]

📲 What

This change adds support for two command-line overrides that make task testing safer and more flexible when working with temporary or uncommitted config:

• eirctl run --import can load additional config files at runtime and merge them into the active configuration, with imported entries taking precedence on name clashes.
• eirctl run ... --context overrides the context assigned to a task for a single invocation, without requiring the tracked config file to be edited.

This is intended to support testing tasks in alternate contexts or with local config overlays while keeping the checked-in configuration unchanged.

🤔 Why

When a task needs to be validated in another execution context, or when a developer wants to try a local override without committing it to the repo, the command-line interface previously offered no clean way to do so.

The result was friction in local development and a higher risk of accidentally persisting temporary configuration changes. The update keeps runtime overrides explicit and scoped to a single invocation.

🛠 How

• Added repeatable --import support to the eirctl run flow, merging imported config files into the current config with override precedence.
• Added --context handling for task execution so the selected task can run with an alternate context for that invocation only.
• Guarded against using --context when executing pipelines, returning a clear validation error.
• Added CLI regression coverage for import precedence and context override behavior.
• Updated the user documentation to describe both features.

👀 Evidence

• Added command coverage in cmd/eirctl/run_test.go
• Added CLI import override fixture: cmd/eirctl/testdata/cli-import-override.yaml
• Updated docs: docs/import.adoc, docs/tasks.adoc

🕵️ How to test

# Override the task context for one invocation

eirctl run task task:context:override --context context:env --raw

# Merge an additional config file at runtime

eirctl run task task:from:cli:import --import testdata/cli-import-override.yaml --raw

# Run the focused command test suite

go test ./cmd/eirctl/...

Expected result:

• the task runs using the overridden context
• imported tasks/contexts become available without changing the base config
• the relevant CLI tests pass

✅ Acceptance criteria checklist

• Linked the related issue or explained why one is not needed.
• Added or updated tests, or explained why tests are not applicable.
• Updated documentation, examples, schemas, or release notes where applicable.
• Ran the relevant linting, test, and validation checks successfully.
• Checked that the change does not expose secrets or weaken security controls.
• Rebased or merged the latest main and re-tested where needed.
• Confirmed the change meets the repository coding standards.