fix: bash 3.2 fractional read timeouts + CI portability lint

[crgeee]

Summary

You hit read: 0.01: invalid timeout specification when pressing Enter on an empty command-mode prompt.

Root cause: macOS default /bin/bash is 3.2 (Apple froze it pre-GPLv3). Bash 3.2 only accepts integer read -t timeouts; the dashboard had a read -t 0.01 for "refresh-now" semantics that worked on bash 4+ in development but errored on the actual installed bash.

There was also a second fractional read -t 0.05 for distinguishing lone Esc from arrow-key escape sequences — the same bug, I missed it.

Two fixes

1. Drop the 0.01s read entirely. When the refresh interval has elapsed, just call _dashboard_refresh_cache and continue — no read needed. Eliminates drift too.
2. _read_short_peek helper for the Esc disambiguation. Branches on a single BASH_HAS_FRACTIONAL_TIMEOUT flag set at script load. 50ms on bash 4+, non-blocking -t 0 on bash 3.2 (arrow-key follow-up bytes are already buffered when we reach the peek, so it works either way).

CI: new portability lint

To catch this class at PR time, new bash32-portability job greps for patterns that break on bash 3.2:

• read -t <fractional>
• mapfile / readarray
• ${var^^} / ${var,,} case conversions
• declare -n / local -n namerefs
• read -i (initial buffer)

Lines tagged # bash4-ok (gated uses) and pure comment lines are skipped. The helper that intentionally uses read -t 0.05 carries the bash4-ok annotation.

This is the second time I've shipped a bash-3.2 issue (first was read -e -i in PR #6). The CI lint catches both retroactively and prevents future ones.

Test plan

• All 78 bats tests pass on bash 5 + macOS bash 3.2
• shellcheck clean
• Portability lint passes on this branch
• Manually verified the read -t 0.01 path is gone
• CI: new bash32-portability job passes
• Test the dashboard interactively after merge — the original repro (Enter on empty prompt) should no longer throw

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Fixes interactive dashboard input handling to be compatible with macOS’s default Bash 3.2 (which rejects fractional read -t timeouts) and adds CI enforcement to prevent future Bash-4+ portability regressions.

Changes:

• Introduce a Bash-version capability flag and _read_short_peek helper to safely disambiguate lone Esc vs escape sequences across Bash 3.2 vs 4+.
• Remove the fractional read -t 0.01 refresh behavior by refreshing immediately when the interval elapses (no read needed).
• Add a new GitHub Actions portability-lint job that flags common Bash-4+ constructs (fractional read -t, mapfile, ${var^^}, namerefs, read -i) unless annotated with # bash4-ok.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
gh-runner-status	Adds Bash version capability detection + _read_short_peek, and removes fractional read timeout usage in the dashboard loop.
.github/workflows/ci.yml	Adds a new bash32-portability CI job to detect Bash-3.2-incompatible patterns early.

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