Seed default config on install; share defaults JSON with runtime

The defaults now live in a single file, scripts/config.default.json:

- src/config.ts imports it via 'with { type: "json" }' and derives
  DEFAULT_CONFIG (with seconds->ms conversion at the boundary), so the
  CLI help text always matches what the seeded user config contains.
- scripts/install.sh copies the same file to
  $XDG_CONFIG_HOME/move/config.json only if no file is already there.
  Existing configs (yours or from a previous install) are never
  overwritten.
- scripts/uninstall.sh does not touch the user config file at all,
  following the strict Unix convention. It does print a one-line
  notice pointing at the path so the user can rm -rf the dir
  themselves if they want a fully-clean removal.
- tsconfig.json gains resolveJsonModule:true so tsc accepts the JSON
  import.
- A small runtime assertion in src/config.ts (assertSeedShape) fails
  loudly if the seed file is missing keys or has wrong types.
- README Configuration section documents the seed behavior; Uninstall
  section documents the leave-config-behind policy with the rm-it-
  yourself command; Files table gains scripts/config.default.json.

scripts/install.sh

@@ -14,15 +14,19 @@
 #   5. Download the source tarball from Gitea, extract under the install dir.
 #   6. `bun install --production` (skips devDependencies).
 #   7. Drop a small wrapper script as `move` on the user's bin dir.
-#   8. Verify PATH, surface macOS Accessibility hint, print final status.
+#   8. Seed the user's config file with defaults, only if one doesn't already
+#      exist at $XDG_CONFIG_HOME/move/config.json.
+#   9. Verify PATH, surface macOS Accessibility hint, print final status.
 #
 # Env vars (all optional):
-#   MOVE_VERSION  Branch or tag to install. Default: master.
-#   MOVE_FORCE    Set to 1 to reinstall even if the version marker matches.
-#   XDG_DATA_HOME Source install root (default $HOME/.local/share).
-#                 Final source location is $XDG_DATA_HOME/move.
-#   XDG_BIN_HOME  Wrapper install root (default $HOME/.local/bin).
-#                 Final binary location is $XDG_BIN_HOME/move.
+#   MOVE_VERSION    Branch or tag to install. Default: master.
+#   MOVE_FORCE      Set to 1 to reinstall even if the version marker matches.
+#   XDG_DATA_HOME   Source install root (default $HOME/.local/share).
+#                   Final source location is $XDG_DATA_HOME/move.
+#   XDG_BIN_HOME    Wrapper install root (default $HOME/.local/bin).
+#                   Final binary location is $XDG_BIN_HOME/move.
+#   XDG_CONFIG_HOME User config root (default $HOME/.config).
+#                   Default config file path is $XDG_CONFIG_HOME/move/config.json.
 #
 # POSIX sh; no bashisms.
 
@@ -37,6 +41,8 @@ MOVE_FORCE="${MOVE_FORCE:-0}"
 
 INSTALL_DIR="${XDG_DATA_HOME:-$HOME/.local/share}/move"
 BIN_DIR="${XDG_BIN_HOME:-$HOME/.local/bin}"
+CONFIG_DIR="${XDG_CONFIG_HOME:-$HOME/.config}/move"
+CONFIG_FILE="$CONFIG_DIR/config.json"
 
 die() {
     printf 'Error: %s\n' "$1" >&2
@@ -44,14 +50,14 @@ die() {
 }
 
 # Refuse to operate on a directory that points somewhere catastrophic.
-# `INSTALL_DIR` derives from XDG_DATA_HOME, a broadly-scoped env var the
-# user could conceivably set to anything; the install path always
-# culminates in `.../move`, but a malformed XDG_DATA_HOME could still
-# resolve to something like '/move' which we don't want to `rm -rf`.
-assert_safe_install_dir() {
-    case "$INSTALL_DIR" in
+# The XDG_* env vars are broadly-scoped and the user could set them to
+# anything; our paths always culminate in `.../move`, but a malformed
+# XDG var could still resolve to something like '/move' which we don't
+# want to `rm -rf` or otherwise mass-write into.
+assert_safe_dir() {
+    case "$1" in
         '' | '/' | "$HOME" | "$HOME/" | '/move')
-            die "refusing to operate on INSTALL_DIR='$INSTALL_DIR' (too broad)"
+            die "refusing to operate on '$1' (too broad)"
             ;;
     esac
 }
@@ -96,7 +102,7 @@ printf '==> Using bun %s\n' "$BUN_VERSION"
 
 # --- Idempotence check -------------------------------------------------------
 
-assert_safe_install_dir
+assert_safe_dir "$INSTALL_DIR"
 
 if [ "$MOVE_FORCE" != "1" ] && [ -f "$INSTALL_DIR/.installed-version" ]; then
     CURRENT=$(cat "$INSTALL_DIR/.installed-version" 2>/dev/null || printf '')
@@ -152,6 +158,33 @@ chmod +x "$WRAPPER"
 
 printf '%s\n' "$MOVE_VERSION" > "$INSTALL_DIR/.installed-version"
 
+# --- Seed user config file (only if absent) ----------------------------------
+#
+# The defaults file shipped with the source tree (scripts/config.default.json)
+# is also the single source of truth for the runtime defaults loaded by
+# src/config.ts, so seeding a fresh user file from the same place keeps the
+# CLI behavior and the user-visible config in sync.
+#
+# Strict policy: never overwrite an existing user config. The uninstaller
+# follows the matching policy of never removing it; together that
+# preserves user customizations unconditionally across (re)installs and
+# uninstalls.
+
+assert_safe_dir "$CONFIG_DIR"
+SEED_SRC="$INSTALL_DIR/scripts/config.default.json"
+
+if [ ! -f "$SEED_SRC" ]; then
+    die "default config seed missing from install tree: $SEED_SRC"
+fi
+
+mkdir -p "$CONFIG_DIR"
+if [ ! -e "$CONFIG_FILE" ]; then
+    cp "$SEED_SRC" "$CONFIG_FILE"
+    printf '==> Wrote default config to %s\n' "$CONFIG_FILE"
+else
+    printf '==> Config already exists at %s; leaving it alone\n' "$CONFIG_FILE"
+fi
+
 # --- PATH sanity check -------------------------------------------------------
 
 case ":$PATH:" in