fix(cli): preserve configured Mint host origin

[Zhao0335]

What does this PR do?

Preserves an operator-provided MINT_PASCAL_HOST_ORIGIN when the CLI starts the managed editor process, while retaining the existing pascal.localhost URL as the fallback when no value is configured.

Adds a regression test that starts the managed runtime and verifies the origin received by the spawned editor process.

Fixes #765

How to test

1. Run: bun --cwd packages/cli test src/runtime.test.ts --test-name-pattern "preserves a configured Mint host origin"
2. Run: bun --cwd packages/cli run check-types
3. Run: bun --cwd packages/cli run build

Local verification: the targeted regression test, CLI TypeScript checks, CLI build, and Biome checks for both changed files pass. The full Windows test run reaches the repository's existing platform-specific failures around POSIX permission bits, process-command verification, and URL pathname globbing; the new test passes in that run.

Screenshots / screen recording

Not applicable; this changes CLI process environment propagation only.

Checklist

• I've tested this locally with bun dev (not applicable to this CLI-only change)
• My code follows the existing code style (checked with Biome)
• I've updated relevant documentation (not applicable; behavior is covered by a regression test)
• This PR targets the main branch

---

Note

Low Risk
Small CLI environment propagation change with a targeted regression test; no auth or data-path changes.

Overview
When the CLI spawns the managed editor, MINT_PASCAL_HOST_ORIGIN is no longer forced to the local pascal.localhost URL. It now uses an operator-set value from the environment when present, and only falls back to state.url when unset.

A regression test starts the managed runtime with MINT_PASCAL_HOST_ORIGIN configured and asserts the spawned editor process sees that origin (via a test-only /mint-origin handler on the fake runtime server).

^{Reviewed by Cursor Bugbot for commit 7c07eaf. Bugbot is set up for automated code reviews on this repo. Configure here.}

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