Expand claw init imports across runner families

[mostlydev]

Follow-up from #230 / PR #234. The first import implementation supports same-runtime imports. Cross-runtime imports should remain explicit follow-up work rather than being implied by the initial claw init --from surface.

Acceptance criteria:

• Document which source/target runner pairs are supported, unsupported, or lossy.
• Add translation tests for at least the first cross-runtime pair before enabling it in the CLI.
• Preserve explicit warnings for settings that cannot be translated faithfully.
• Keep the generated claw-pod.yml and Clawfile output deterministic for repeat imports.

Notes:

• Start from the existing issue claw init --from should support same-runtime and cross-runtime imports #230 plan and PR Support same-runtime imports in claw init #234 implementation.
• Do not silently broaden imports until the behavior is covered by tests and docs.