fix(#67): guard GITHUB_WORKSPACE fallback against empty values

[fullsend-ai-coder]

When GITHUB_WORKSPACE is unset or empty, the workspace-directory fallback for companion script lookup expands to absolute paths /scripts and /.fullsend/scripts, probing the filesystem root. Wrap each fallback loop in a non-empty guard so the loop only runs when GITHUB_WORKSPACE is actually set and non-empty.

Affected files:

• scripts/post-code.sh (resolve/install script fallback)
• scripts/post-fix.sh (resolve/install and process-fix-result
  fallbacks)
• scripts/pre-code.sh (resolve/install script fallback)
• scripts/pre-fix.sh (resolve/install script fallback)

---

Closes #67

Post-script verification

• Branch is not main/master (agent/67-guard-workspace-fallback)
• Secret scan passed (gitleaks — 284bcfd9c77b44e00222290bd6b94e45caff32c5..HEAD)
• Pre-commit hooks passed (authoritative run on runner)
• Tests ran inside sandbox

[fullsend-ai-retro]

🤖 Finished Retro · ✅ Success · Started 7:10 AM UTC · Completed 7:20 AM UTC
Commit: a9fcbde · View workflow run →

[fullsend-ai-retro]

Retro: PR #69 — guard GITHUB_WORKSPACE fallback against empty values

Timeline

1. Jul 8, 15:51 — Retro agent (from PR fix: fall back to workspace scripts dir for script companions #41 retro) files issue #67: GITHUB_WORKSPACE fallback probes root filesystem when unset.
2. Jul 8, 15:52–15:56 — Triage agent runs: classifies as low-severity bug, labels ready-to-code, provides exact fix recommendation with code snippets and all 4 affected files.
3. Jul 8, 15:57–16:07 — Code agent implements fix: +48/−38 across pre-code.sh, pre-fix.sh, post-code.sh, post-fix.sh. Creates PR #69.
4. No review agent ran — known dispatch gap for code-agent PRs (dispatch: ADR 0054 authorization gate blocks review dispatch for coder-bot PRs fullsend#2674).
5. Jul 10, 10:50 — Human reviewer approves silently; auto-merge enabled.
6. Jul 13, 06:59 — Human force-pushes branch (rebase). Added to merge queue at 07:04, merged at 07:08.

Assessment

What went well: The full pipeline (retro → issue → triage → code → PR → merge) completed with zero rework. The retro agent correctly identified all 4 affected files when creating issue #67. The triage agent produced an accurate analysis in 5 minutes. The code agent implemented the fix in 10 minutes with a correct, minimal change. The code agent's PR was approved on first submission.

Known gaps (already tracked):

• Review agent dispatch gap for code-agent PRs — tracked in dispatch: ADR 0054 authorization gate blocks review dispatch for coder-bot PRs fullsend#2674, discussed in issue #104.
• 5-day merge latency dominated by human review wait — tracked in issue #104.
• Duplicated GITHUB_WORKSPACE fallback pattern across scripts — tracked in issue #70 (CSMA lib extraction). The workspace fallback is a separate duplication instance but the same structural pattern.

Novel finding: Pre-scripts (pre-code.sh, pre-fix.sh) have no test files and are absent from the Makefile's script-test target. The GITHUB_WORKSPACE guard fix in these files has zero regression test coverage. See proposal below.

Proposals filed

• Add unit test files for pre-scripts (pre-code.sh, pre-fix.sh, and others) (in fullsend-ai/agents)