fix(cli): baseline path join + per-statement EXPLAIN

[c2j]

Summary

Fixes two bugs found during UserGuide × testcases verification:

1. fix(cli): join git_repo when resolving baseline-discovered file paths #24 — Baseline-discovered files are repo-relative; when git_repo is not . (e.g. c2j/ogagila), reads failed with No such file. Paths are now joined with git_repo. file_diff runs under repo_path so --diff-aware stays consistent.

2. fix(cli): run EXPLAIN per SQL statement, not whole multi-statement file #25 — Multi-statement SQL files ran a single EXPLAIN on the whole file; one failure aborted all plan analysis. Statements are split via ogsql-parser and each explainable DML is EXPLAINed independently (per-statement failures only warn).

Also: clippy manual_contains in cr-core filter (CI hygiene).

Test plan

• cargo test -p cr-cli (includes new unit tests for path join + statement split)
• cargo test -p cr-git
• cargo clippy -p cr-cli -p cr-git -p cr-core -- -D warnings --no-deps
• Manual (with testcases + pagila):

  cd testcases
  coderc audit --project ogagila --baseline main --no-db
  # should read c2j/ogagila/... files without No such file
  coderc audit --project ogagila --files path/to/multi.sql
  # multi-select file should produce SCAN/JOIN findings when DB up

Closes #24
Closes #25

[github-actions]

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项目: self

执行摘要

指标	值
健康度评分	🟢 100/100（优秀）
问题总数	0（🔴 Critical: 0 / 🟡 Warning: 0 / 🔵 Info: 0）
审核分支	origin/main
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✅ 审核通过，未发现问题。