declare multiple components in one manifest

[joshua-temple]

Problem / why

With the component parser and component-major model in place, the components: block needs its
full field set wired so each component owns its complete pipeline: its paths, tag_prefix,
triggers, builds, and deploys. This makes trigger, build, and deploy scoping local to the
component.

Scope

This PR does:

• Complete ComponentConfig (internal/config/types.go) to carry Paths []string,
  TagPrefix string, Triggers []string, Builds []BuildConfig, Deploys []DeployConfig,
  and an optional Environments []string placeholder (env subsets are implemented in X1).
• Add resolvers: GetComponentTagPrefix(name) (component prefix, falling back to the
  manifest-level prefix), ComponentNames(), ComponentTriggers(name).
• Extend the component validator (F2) to fully validate the nested ownership: each component's
  builds and deploys are well-formed, paths are clean, and triggers resolve.

This PR does NOT:

• Implement per-component version math (V2) or per-component file generation (V3).
• Implement environment subsets (X1) beyond parsing the field.
• Touch the single-component path.

Files / areas touched

• internal/config/types.go - full ComponentConfig, new resolvers.
• internal/config/validate_components.go - full nested ownership validation.

Tests and coverage required

• Unit tests for a two-component manifest with full per-component pipelines.
• Validation tests: malformed per-component builds / deploys / paths rejected.
• A test that a manifest with no components: block still loads as the single default
  component identically.

Acceptance criteria

• A components: block with nested paths / tag_prefix / triggers / builds / deploys
  parses and validates.
• Per-component resolvers return the right scoped values.
• Single-component manifests are unaffected.

Dependencies

Blocked by the component-model foundation milestone (F1-F5).

[joshua-temple]

Implemented and merged via #507.