fix(core): normalize model base URL to origin

[XXPermanentXX]

Summary

• normalize model-service Base URLs to their URL origin
• remove all user-provided path, query, and fragment components while preserving explicit ports
• update config, resolver, persistence, UI, and E2E expectations
• keep bl config agent provider Base URL behavior unchanged

Why

Users may copy a model-specific endpoint such as https://example.com/api/v1/agentstudio and provide it as base_url. The previous suffix-based normalization preserved unknown paths, so the CLI could append its own endpoint path to an already specific API path.

The model-domain base_url contract is now unambiguous: it is the service origin, and CLI commands append their own API paths.

Impact

https://example.com/api/v1/agentstudio now normalizes to https://example.com. Path-mounted gateway prefixes are no longer retained. URLs with explicit ports, such as http://localhost:8080/path, normalize to http://localhost:8080.

Validation

• vp test run packages/core/tests/model-base-url.test.ts packages/core/tests/config-store.test.ts packages/core/tests/config-priority.test.ts packages/core/tests/index.test.ts packages/commands/tests/config-ui.test.ts packages/commands/tests/e2e/config.e2e.test.ts — 87 tests passed
• vp check — formatting, lint, and type checks passed
• pre-commit skill reference generation and checks passed