feat: upload command

[davideast]

This PR refactors the image-only upload-image CLI command into a universal upload command, enabling seamless uploads of design assets (PNG, JPG, JPEG, WEBP) as well as interactive HTML files via the updated @google/stitch-sdk client. Additionally, it introduces runtime schema-repair mechanisms in the SDK layer to guarantee client-side resilience against incomplete backend schema payloads.

What Changed

1. Universal upload Command Slice (src/commands/upload/)

• command.ts: Standardizes option parsing (--project, --file, --title) using Commander. Implements lazy, dynamic imports to isolate connection side-effects and boost CLI boot speeds. Wire-connects the command action to the unified project.upload() SDK method.
• handler.ts: Generalizes the business logic layer to process any valid asset. Maintained strong Dependency Injection ports (UploadFn) for isolated test mapping, transforming errors into result-oriented, typed status values without throwing.
• spec.ts: Hardens input validation using Zod (UploadInputSchema). Features directory traversal guardrails (..) to reject malicious path escalations before shell or disk operations.

2. Core SDK Resilience Layer (Schema Repair)

• Patched the @google/stitch-sdk tool discovery sequence (StitchToolClient.listTools()).
• Intercepts remote tool schemas at runtime and injects missing $defs declarations (e.g., ScreenInstance, File). This prevents strict AJV validation crashes during discovery and tool compilation, shielding developers and CI setups from malformed upstream schemas.

3. Test Suite Alignment & Verification

• Renamed and refactored all test assets inside tests/commands/upload/.
• Hardened mock definitions and assertions to cover robust file inputs and the new results structure.
• Verified full test compliance: all 567 unit and integration tests pass cleanly with 100% test health.

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Files Changed

New CLI Command Slice

• src/commands/upload/command.ts — Options parsing, lazy import, and SDK wiring
• src/commands/upload/handler.ts — Generalized asset handling and DI upload mappings
• src/commands/upload/spec.ts — Zod input validation and directory traversal guards

Unit & Integration Test Suites

• tests/commands/upload/handler.test.ts — Comprehensive error classification and mock upload tests
• tests/commands/upload/spec.test.ts — Input schema constraint and path-traversal verification

Underlying SDK Patches

• packages/sdk/src/client.ts — On-the-fly schema repair interceptor