#891 test: add shellcheck disable and spec for rtk-rewrite.sh

Summary

• Add # shellcheck disable=SC2001 to config/claude/rtk-rewrite.sh — the sed patterns use ^ (start-of-string anchor) which bash parameter expansion cannot replicate
• Add spec/rtk_rewrite_spec.sh with 26 tests covering guards, skip conditions, git/gh/cargo/file/JS/Python/Go rewrites, env prefix preservation, and output format
• Register rtk-rewrite.sh in spec/coverage_spec.sh coverage list

Test plan

• make shell-lint passes (0 warnings)
• make shell-test passes (523 examples, 0 failures)

🤖 Generated with Claude Code

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Summary by cubic

Allow sed-based rewrite patterns in rtk-rewrite.sh and add a comprehensive spec to lock down behavior. Suppresses a false shellcheck warning, expands coverage, keeps CI passing, and formats the new spec.

• Bug Fixes

  • Disable shellcheck SC2001 in rtk-rewrite.sh.
  • Mock the rtk binary in the spec to avoid guard exits in CI.
  • Format rtk_rewrite_spec.sh for consistency.

• New Features

  • Add spec/rtk_rewrite_spec.sh with 26 tests for guards, skip conditions, rewrites (git, gh, cargo, file ops, JS/TS, Python, Go), env var preservation, and JSON output.
  • Register rtk-rewrite.sh in spec/coverage_spec.sh.