Description

Fixes the TODO in installer/mod.rs that noted link_type: Some(LinkType::HardLink) was always
hardcoded.

Problem

PrefixRecord.link.link_type was always written as HardLink, even when:

• hard links are impossible (cross-device, NFS, CIFS…)
• the caller explicitly set LinkOptions { allow_hard_links: Some(false) }

The actual file linking via link_package_sync was already correct (it probes filesystem capability
and falls back to copies). Only the metadata recording was wrong.

Solution

• Expose can_create_hardlinks_sync as pub(crate) so the installer can call it
• Before moving install_options into link_package_sync, capture allow_hard_links
• After linking, resolve the effective value (explicit option → filesystem probe)
• Record HardLink when hard links were used, Copy otherwise

Fixes #2168

How Has This Been Tested?

Two new unit tests in installer::tests:

• test_link_type_recorded_correctly — allow_hard_links: Some(false) → Copy in conda-meta
• test_link_type_hardlink_when_forced — allow_hard_links: Some(true) → HardLink in conda-meta

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added sufficient tests to cover my changes.