Clone strategy live smoke for full, partial, and sparse checkout

[BramVR]

Parent: #70

What to build

Add live smoke coverage for clone strategy behavior: full clone baseline, partial clone opt-in, and sparse checkout opt-in.

This should prove the Git Operations layer can select and explain the clone strategy without weakening the MVP full-clone default.

Acceptance criteria

• Full clone live smoke uses a public remote and verifies normal checkout provenance.
• Partial clone smoke runs only when local Git and the remote support it; unsupported cases become SKIP unless live strict mode is enabled.
• Sparse checkout smoke verifies requested paths are present and unrelated paths are absent or not materialized.
• The selected clone strategy is recorded in state, command output, and report metadata.
• Fallback from partial/sparse to full clone is explicit and user-visible when configured that way.
• No smoke depends on a source checkout or user Git config.
• Docs explain when to use each strategy smoke and which one is required for PR CI.

Blocked by

• Live e2e harness guardrails and report mode #88
• Clone Strategy full-clone baseline #84
• Partial clone and sparse checkout opt-in #85

Cost guardrail

• Must stay free: public remotes and standard/local runners only. Partial/sparse unsupported cases SKIP rather than requiring paid infrastructure.