Create Context Builder CLI and authoring/review workflow

[andrewperis]

Parent epic: #5

Summary

Create Context Builder CLI and authoring/review workflow for Context Builder v1.

Ownership and dependencies

• Repositories: platform.
• Depends on: Integrate Context Builder with Prompt SDK v1 and downstream handoff #83.
• Baseline: released Prompt SDK v1.0.0 and Context Package v1.0.0; do not change immutable contract bytes.

Scope and deliverables

• Provide validate, inspect/plan, build and verify/replay commands over explicit request/fixture files using the public Builder API.
• Emit human-readable and machine-readable output with stable exit codes, actionable value-free diagnostics and an offline CI path.
• Document approved runtime credential injection, protected output destinations, package review and external use-authorization handoff.
• Publish synthetic public/private-export examples and a lab → Codex/Platform authoring workflow; no auto-approval, repository mutation or publication command.

Acceptance criteria

• Authors can build and validate a package locally without paid services, private source access or provider calls.
• JSON output and failure exits are tested in subprocesses, including malformed files and missing authority.
• Dry-run/plan has explicitly documented reads and side effects; it is not an authorization bypass.
• Protected bodies require explicit authorized output handling and never appear in routine logs or CI fixtures.

Implementation guardrails

Follow Constitution v1.0.0 at a9cc8a503aa30e17820edc62ac95f7cbe10e0564 and repository boundaries. Add focused tests with implementation; the suite task consolidates rather than postpones testing. Public issues, fixtures and docs use synthetic/already-public material only. Approved private inputs stay behind explicit secure artifact boundaries. No direct Lore checkout, silent declassification, self-approval or canon promotion.