Harden tangent with shell script hooks

[rfreel]

Motivation

• Ensure bash scripts under scripts/ralph/ meet basic quality rules (shellcheck/shfmt) before merge.
• Make the local loop and CI share a single tangent runner to avoid drift between local and CI checks.
• Improve failure provenance so failing checks capture an error vector and produce a short ledger entry pointing to loop/last_error.txt.

Description

• Added shellcheck and shfmt local hooks targeting ^scripts/ralph/.*\.sh$ in .pre-commit-config.yaml.
• Added scripts/ralph/tangent.sh which runs pre-commit run --all-files and uses safe shell flags (set -euo pipefail).
• Updated scripts/ralph/loop.sh to invoke bash scripts/ralph/tangent.sh (capturing output to a temp file) instead of running pre-commit inline, and to write the error vector into loop/last_error.txt and append a short [ERROR] line to loop/log.txt on failure.
• Recorded PR progress by appending an [OK] line to loop/log.txt and a PR-1 entry to progress.txt.

Testing

• No automated tests were run for this change.

---

Codex Task

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: f8317cfd2a

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Allow loop to proceed without local pre-commit

Because tangent.sh unconditionally runs pre-commit under set -e, a machine without pre-commit installed now exits 127 and forces loop.sh to fail. That breaks the documented “CI-enforced” path (README.md lines 5 and 10: back-pressure can come from CI and PR-only flow is allowed), which previously tolerated a missing local pre-commit. Consider checking for pre-commit and emitting a non-fatal message so the local loop can still run when relying on CI.

Useful? React with 👍 / 👎.

[rfreel]

c