huskies: done 474_story_per_file_test_coverage_report_with_improvement_targets

.huskies/work/5_done/474_story_per_file_test_coverage_report_with_improvement_targets.md

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+---
+name: "Per-file test coverage report with improvement targets"
+---
+
+# Story 474: Per-file test coverage report with improvement targets
+
+## User Story
+
+As a developer, I want a standardised JSON output format for test coverage so that any language's coverage tool can produce it and huskies can read it without language-specific logic.
+
+## Acceptance Criteria
+
+- [ ] Define a standard `.coverage_report.json` format: `{ "overall": float, "threshold": float, "files": [{ "path": string, "coverage": float }] }`
+- [ ] Update huskies' own `script/test_coverage` to write `.coverage_report.json` in this format (Rust via `cargo llvm-cov --json`, frontend via vitest)
+- [ ] `coverage` bot command reads `.coverage_report.json` and shows overall percentage plus top 5 lowest-covered files as improvement targets
+- [ ] Document the `.coverage_report.json` format in `.huskies/README.md` so other projects can produce it from any language
+- [ ] Huskies server has zero language-specific coverage logic — all intelligence is in the project's `script/test_coverage`
+
+## Out of Scope
+
+- TBD