elegance: install.sh has no source-file precheck — partial install + lying --dry-run on a missing/renamed theme

[Antawari]

DO NOT MERGE — fleet quality burn unit. Review/merge is the user's call.

The claim this satisfies

install.sh ran cp -f "$HERE/themes/<file>" <target> for five sources with no existence guard.

Reproducer (partial install): delete themes/candyfactory-parlor-light.ron, run ./install.sh. Under set -e the dark theme copies first, then cp errors cannot stat … No such file or directory and the script aborts exit 1 — leaving a half-installed theme set in ~/.config/cosmic with no cleanup and no typed message.

Reproducer (--dry-run lies): ./install.sh --dry-run for the same missing source printed all five would: cp lines and exited 0, falsely reporting success — because run() only echoes in dry mode and never touches the filesystem, so the missing source is never noticed.

Both reproducers confirmed RED on the unmodified installer before the fix (1 partial file written; dry-run exit 0).

The fix

A precheck that asserts all five sources exist (and fails fast with one clear typed message before any copy) closes both paths. It runs in both normal and dry-run modes, so --dry-run can no longer lie. Sources are named once and shared with the copy block, so the precheck and the copies can never drift (DRY). The --uninstall, --help, and happy-path install behaviours are unchanged.

TDD

tests/test_install_precheck.sh (new, dependency-free bash) was written RED-first and pins:

• real install over a missing source aborts non-zero and writes nothing (no partial install)
• --dry-run over a missing source exits non-zero and prints no would: cp preview (dry-run no longer lies)
• the abort message names the missing file
• happy-path regression guards: full real install still lands the set; full --dry-run still previews and exits 0

Wired into .github/workflows/checks.yml. Complements the existing tests/test_install.sh (happy-path integration) — no overlap, no existing test weakened.

Gate (local, mirrors CI)

• shellcheck install.sh tests/*.sh — clean
• test_accent_palettes.sh 14/14 · test_theme_rons.sh 13/13 · test_install_precheck.sh 5/5 · test_install.sh 7/7 — 39/39 green

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