Add automated test harness for bump_version.sh

[stslex]

Context

.github/scripts/bump_version.sh is in the hot path of every release. It parses the TOML, performs an atomic rewrite, and is the single point where versions get bumped. One edge-case bug (CRLF line endings, BOM, trailing whitespace, an unusual quote style sneaking into the TOML) wedges every future cut.

The script was smoke-tested by hand during the Stage 7 migration (release happy path, hotfix happy path, malformed versionName rejection with file-unchanged assertion, missing/invalid --mode rejection, trailing-newline preservation), but those tests were never committed. They will silently regress on the next edit.

What's needed

1. Add .github/scripts/bump_version_test.sh (bash or bats) covering at least:

   • --mode=release happy path (e.g. 1.5.0 / 42 → 1.6.0 / 43).
   • --mode=hotfix happy path (1.6.0 / 43 → 1.6.1 / 44).
   • Missing --mode and invalid --mode=<other> are rejected with a non-zero exit and a usage message.
   • Malformed versionName (e.g. "1.5") is rejected and the input file is left byte-identical.
   • Trailing-newline preservation: file ending with \n retains the \n; file ending without \n retains no \n.
   • (Stretch) CRLF line endings are tolerated, or are explicitly rejected with a clear error.

2. Wire the test into CI so it runs on every PR that touches .github/scripts/**. Easiest path: add a job (or a step in pr_guard.yml) gated by a paths: filter on .github/scripts/**.

References

• .github/scripts/bump_version.sh.
• documentation/release-flow.md §4.1, §4.2 — TOML format and bump rules the script implements.

[stslex]

2026-08-21 audit against dev e0ada8f: still open. bump_version.sh exists, but no bump_version_test.sh or equivalent automated harness exists, and no workflow condition runs script tests when .github/scripts changes. The original acceptance cases remain current. Release impact: non-blocking release-pipeline regression risk.