[LE0-Lin]

Summary

• Distinguish an absent repository-config entry from a dangling/cyclic/unreadable source instead of silently applying compatibility defaults.
• Require config to resolve to a regular file inside its selected root before content reads; open the resolved target as strict UTF-8. Keep internal file aliases and explicitly selected root aliases. Sanitize source metadata/resolution/read failures without target paths or raw I/O details.
• Use the existing shared loader for scan, feedback, both comparison trees and doctor. Threshold overrides cannot bypass invalid sources. Preserve baseline-governed policy with tracked relative internal config links, including in temporary Git worktrees.
• Add 16 focused contracts for invalid sources before reads, normal/internal/root-alias controls, source error privacy, report preservation and real Git baseline/candidate rejection with worktree cleanup. Extend installed-wheel acceptance across console aliases/module/doctor/compare/feedback where the host permits symlinks.
• Synchronize English/Simplified/Traditional core guidance, external-link migration and Git worktree compatibility. Keep non-atomic/concurrent-replacement, hard-link and mount limits explicit. Workflow-only setup and unscored guardrails remain separate interfaces.
• Source-only change: no release/version/tag/v0 update, scoring/default change for valid inputs, frozen-research rewrite or external maintainer contact.

Verification

• Reproduced the old dangling-link fallback/external-read behavior before implementation; regression log retained locally.
• Full Windows suite: 532 tests, 520 passed and 12 platform skips.
• Linux policy-source suite: all 16 passed, including FIFO and real Git link fixtures.
• Wheel/source-distribution build and all 16 installed-wheel acceptance journeys passed offline; link controls disclose platform availability.
• Demo remains F 56. These engineering contracts are not independent accuracy, adoption or policy-adequacy evidence.
• Runtime source identity: bca1d4976d359c2f6e37a7068c077691461d8fc117d3df6a6ab3fdb5a10f82ef.
• Exact-head cross-platform CI and pinned-repository replay run before merge; expected operational rejection remains distinct from a clean scan.