Make development-environment preparation private to the Issue Run

[rochecompaan]

Parent

#154

What to build

Internalize lazy workspace creation and development-environment preparation so environment readiness and remediation stops remain part of one ordered Issue Run lifecycle rather than a callable stage.

Acceptance criteria

• Development-environment preparation is private to the Issue Run and cannot be invoked as a supported independent stage.
• Workspace creation remains lazy and preserves existing recovery, progress, Pi session, and checkpoint behavior.
• Development-environment-not-ready remains an explicit compatible result rather than an unexpected fault.
• Equivalent behavior is verified through runOneIssue scenarios before redundant direct-stage tests are removed.

Blocked by

• Make planning private to the Issue Run #160 — Make planning private to the Issue Run