feat(pipeline): add parameters support to luca run

[albertodebortoli]

Description

• Adds a parameters: block to pipeline YAML files, allowing pipelines to declare named input parameters with optional descriptions and default values.
• Values are supplied at invocation time via --param KEY=VALUE (repeatable) and substituted into task commands using ${name} syntax before execution.
• A required parameter (no default:) causes a clear error if not supplied via --param.
• Closes no specific issue; this is new standalone functionality building on the existing luca run pipeline feature.

Design decisions:

• ParameterResolver is a separate Core component (protocol + struct) following the existing DI pattern, making it independently testable and injectable.
• Template substitution (${key}) is applied in PipelineRunner just before subprocess execution, keeping the pipeline model immutable.
• The PipelineRunning protocol gains a parameters: overload via a protocol extension default, so all existing callers remain unchanged.
• --param values with = in the value (e.g. URLs) are handled correctly via maxSplits: 1.

Type of Change

• Feature

How Has This Been Tested?

• Added / updated unit tests
• Manually tested locally (describe)
• Tested on macOS (arch: arm64)

New tests added (32 tests across 4 files):

• PipelineLoaderTests — parameters: block decoded from YAML, nil when absent, full fixture round-trip
• ParameterResolverTests — 11 tests covering all resolution paths: defaults, required params, unknown params, multiple params, error descriptions
• PipelineRunnerTests — 4 substitution tests: single token, multiple tokens, empty params (command unchanged), unknown token (left as-is)

Manual smoke tests:

# Default value used
luca run --file pipeline.yml
# → echo "hello, world"

# CLI override
luca run --file pipeline.yml --param greeting=hi
# → echo "hi, world"

# Dry-run shows parameters block with (default)/(override) labels
luca run --file pipeline.yml --dry-run --param greeting=hi

# Unknown param → clear error
luca run --file pipeline.yml --param unknown=val
# → Error: Unknown parameter 'unknown'. It is not declared in the pipeline's parameters block.

# Required param missing → clear error
luca run --file pipeline.yml
# → Error: Required parameter 'upload' was not provided. Pass it with --param upload=<value>.

Full test suite: 444 tests, all passing.

Screenshots / Demo (if applicable)

Pipeline YAML example:

parameters:
  - name: flavor
    description: Build flavor (debug or release)
    default: debug
  - name: upload
    description: Whether to upload the artifact

tasks:
  - name: Build
    command: build --flavor ${flavor}
  - name: Upload
    command: upload --artifact ${upload}

luca run ci --param flavor=release --param upload=true

Checklist

• Swift code builds locally (swift build)
• Tests pass locally (swift test)
• Code style / formatting respected
• Documentation updated (README / comments)
• Version / tag alignment considered (if release related)
• PR title follows conventional style (optional)

CI Considerations

• Affects build time notably
• Requires new secrets / env vars
• Alters release process

Breaking Changes?

• No

Additional Notes

The when: conditional execution clause (skip tasks based on parameter values) was deliberately deferred to a follow-up iteration to keep this PR focused.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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