Keep the image's Bundler defaults when roast strips BUNDLE_* for subprocesses

[pstrzalk]

Why

PR #45 put the skeleton's gems in the image, and bundle check on a workspace now passes in the generator container and in a plain docker run --user 1000 of the sandbox image. It still failed inside every real sandbox run (project 36, 2026-09-03 22:08: all 116 gems "missing", fix agent reinstalls them, 97s and $0.07 per revision).

Cause: Bundler.with_unbundled_env, used by our verify step and by the roast gem when it spawns the code agent, deletes every BUNDLE_* variable, not only what bundle exec set. That takes the Dockerfile's BUNDLE_PATH and BUNDLE_WITHOUT with it. Without BUNDLE_PATH, Bundler looks under $GEM_HOME/gems instead of $BUNDLE_PATH/ruby/<abi>/gems and reports the whole lockfile missing; without BUNDLE_WITHOUT it wants the development group the image never installs. Reproduced on production:

env inside the sandbox image	bundle check
as shipped	satisfied
BUNDLE_* stripped	every gem missing
only BUNDLE_PATH restored	web-console, bindex missing

What

• Dockerfile: the claude wrapper exports BUNDLE_PATH/BUNDLE_WITHOUT (image defaults, caller values win), so the agent and everything it runs resolve gems. The Bundler ENV block moves above the wrapper so it quotes the same values at build time.
• VerifyRevision.with_clean_bundler_env: restores the same two keys from Bundler.original_env inside with_unbundled_env. The comment claiming Bundler keeps Dockerfile globals is gone.
• AutoRemediate.shell: runs in that scrubbed env too. Under roast's bundle exec its bundle install recipe ran with BUNDLE_GEMFILE=<generator Gemfile>, "completed" in 0.6s against the generator's already-satisfied bundle, and fixed nothing, every revision.
• Tests pin the restore, the dev no-op (no BUNDLE_PATH in the original env → nothing added), and that the parent env is untouched. CHANGELOG 1.5.2.

Verified

• Wrapper generated with the Dockerfile's exact printf commands: sh -n clean; with BUNDLE_* stripped it exports /usr/local/bundle / development; a caller's value wins.
• Bundler.unbundled_env drop confirmed locally (Bundler 4.0.9) and the failure/pass matrix above on production (Bundler 4.0.6).
• Full suite 630 runs green, rubocop clean.

After merge

kamal deploy, then one change request on any project. Expected in kamal app logs --grep 'W2.4\|auto_remediate\|Cost (USD)': four [W2.4] PASS lines, no auto_remediate lines, two cost lines (code agent, docs agent).

🤖 Generated with Claude Code

https://claude.ai/code/session_0117StvHb26xv3MUepWHhcWy