Fix TARBALL_INCLUDE config default drift (7r0, scoped down)

apply_config_defaults fell back to TARBALL_INCLUDE=no while the user-facing
src/shuriken.default.conf documents (and --init writes) TARBALL_INCLUDE=yes.
The two disagreed, so an album generated from a config that omitted the key
silently dropped the tarball despite the documented default saying otherwise.

'yes' is the authoritative default: the original definition was
`declare -r TARBALL_INCLUDE=yes` (tarball inclusion was on from the start);
the ':-no' fallback was introduced later during a refactor and drifted from
the documented intent. Align apply_config_defaults to ':-yes' and add a
comment explaining the invariant and the history.

Tests: add test_tarball_include_default_matches_init_config asserting the
effective default agrees between a fresh --init config and apply_config_defaults
(and is 'yes'); update the omitted-runtime-defaults --print-config expectation
to the corrected 'yes'. bin/shuriken regenerated via just build.

This is the scoped-down drift fix only. The full CONFIG_SPECS registry plus
cfg_get/SHURIKEN_CFG access-layer rewrite proposed in 7r0 remains DEFERRED.

just test, just shellcheck, just check-generated and git diff --check all pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

3 files changed, 53 insertions, 3 deletions

diff --git a/bin/shuriken b/bin/shuriken
index 30cfa56..280d8b6 100755
--- a/bin/shuriken
+++ b/bin/shuriken
@@ -4977,7 +4977,11 @@ apply_config_defaults() {
     THUMB_SUBDIVIDE_PERCENT="${THUMB_SUBDIVIDE_PERCENT:-30}"
     THUMB_FEATURE_PERCENT="${THUMB_FEATURE_PERCENT:-10}"
     SYNC_DELETE="${SYNC_DELETE:-yes}"
-    TARBALL_INCLUDE="${TARBALL_INCLUDE:-no}"
+    # Default 'yes': a tarball of the incoming dir is included in the dist unless
+    # disabled. This must match the documented default in shuriken.default.conf
+    # (TARBALL_INCLUDE=yes) -- it previously drifted to 'no' here. 'yes' is the
+    # original, authoritative default (tarball inclusion was on from the start).
+    TARBALL_INCLUDE="${TARBALL_INCLUDE:-yes}"
     TARBALL_SUFFIX="${TARBALL_SUFFIX:-.tar}"
     TAR_TIMEOUT="${TAR_TIMEOUT:-120}"
     if ! declare -p TAR_OPTS >/dev/null 2>&1; then
diff --git a/src/lib/config.source.sh b/src/lib/config.source.sh
index 67ddade..9dd48ee 100644
--- a/src/lib/config.source.sh
+++ b/src/lib/config.source.sh
@@ -52,7 +52,11 @@ apply_config_defaults() {
     THUMB_SUBDIVIDE_PERCENT="${THUMB_SUBDIVIDE_PERCENT:-30}"
     THUMB_FEATURE_PERCENT="${THUMB_FEATURE_PERCENT:-10}"
     SYNC_DELETE="${SYNC_DELETE:-yes}"
-    TARBALL_INCLUDE="${TARBALL_INCLUDE:-no}"
+    # Default 'yes': a tarball of the incoming dir is included in the dist unless
+    # disabled. This must match the documented default in shuriken.default.conf
+    # (TARBALL_INCLUDE=yes) -- it previously drifted to 'no' here. 'yes' is the
+    # original, authoritative default (tarball inclusion was on from the start).
+    TARBALL_INCLUDE="${TARBALL_INCLUDE:-yes}"
     TARBALL_SUFFIX="${TARBALL_SUFFIX:-.tar}"
     TAR_TIMEOUT="${TAR_TIMEOUT:-120}"
     if ! declare -p TAR_OPTS >/dev/null 2>&1; then
diff --git a/tests/cli.sh b/tests/cli.sh
index eae2f19..5d69684 100755
--- a/tests/cli.sh
+++ b/tests/cli.sh
@@ -251,6 +251,45 @@ test_init_existing_config_fails_without_overwrite() {
     test::teardown
 }
 
+# Guards against config DEFAULT DRIFT for TARBALL_INCLUDE: its documented default
+# in shuriken.default.conf (written verbatim by --init) MUST agree with the
+# fallback applied by apply_config_defaults when the key is unset. These two
+# previously disagreed ('yes' in the conf vs 'no' in apply_config_defaults); the
+# authoritative default is 'yes' (tarball inclusion has been on since the start).
+test_tarball_include_default_matches_init_config() {
+    local init_default
+    local applied_default
+
+    test::setup
+
+    # Value a fresh --init config gives the user (the documented default).
+    (
+        cd "$TEST_TMPDIR"
+        SHURIKEN_DEFAULT_RC="$TEST_TMPDIR/missing" \
+            "$TEST_SHURIKEN" --init >/dev/null
+    )
+    init_default=$(
+        set -euo pipefail
+        # shellcheck disable=SC1090,SC1091
+        source "$TEST_TMPDIR/shuriken.conf"
+        printf '%s\n' "$TARBALL_INCLUDE"
+    )
+
+    # Value apply_config_defaults falls back to when the key is left unset.
+    applied_default=$(
+        set -euo pipefail
+        # shellcheck source=/dev/null
+        source <(sed '$d' "$TEST_SHURIKEN")
+        unset -v TARBALL_INCLUDE || true
+        apply_config_defaults
+        printf '%s\n' "$TARBALL_INCLUDE"
+    )
+
+    test "$init_default" = "$applied_default"
+    test "$applied_default" = yes
+    test::teardown
+}
+
 test_just_install_and_deinstall_with_destdir() {
     local stage_dir
 
@@ -1499,7 +1538,7 @@ RANDOM_SEED=''
 SHUFFLE=no
 SPLASH_PAGE=yes
 STATS_PAGE=no
-TARBALL_INCLUDE=no
+TARBALL_INCLUDE=yes
 TARBALL_SUFFIX=.tar
 TAR_TIMEOUT=120
 TAR_OPTS=( -c )
@@ -6466,6 +6505,9 @@ main() {
         '--init refuses existing config without overwrite' \
         test_init_existing_config_fails_without_overwrite
     test::run_case \
+        'TARBALL_INCLUDE default matches between --init config and apply_config_defaults' \
+        test_tarball_include_default_matches_init_config
+    test::run_case \
         'just install and deinstall supports DESTDIR' \
         test_just_install_and_deinstall_with_destdir
     test::run_case '--clean succeeds' test_clean