round-5 follow-up: completion + i18n sweep

Four user-reported gaps from the round-4 testing pass:

1. Empty-prompt hint reworded from "(no active hint)" to
   "Type a command — press Tab for options, `help` for a
   list" (6 snapshots updated to reflect 80-col truncation).

2. App-lifecycle commands (quit/q, help, rebuild, save/save as,
   new, load, export, import, mode, messages) now flow through
   the DSL parser:
   - 15 new keywords + catalog token entries
   - new Command::App(AppCommand) AST with 11 variants
   - parse-first dispatch in submit() (app commands work in
     both simple and advanced modes)
   - pre-chumsky source-slice for `export <path>` /
     `import <zip> [as <target>]` mirrors the replay precedent
   - UsageEntry registry entries so parse errors surface
     relevant usage templates
   - `mode <bad>` / `messages <bad>` use try_map for the
     friendly "unknown mode/messages" wording

3. DSL completion gaps:
   - `1:n` surfaces as a composite candidate at `add `
   - --all-rows / --create-fk / --force-conversion /
     --dont-convert surface as new CandidateKind::Flag
     candidates (coloured with tok_flag in hint panel)
   - filter_clause .labelled() wrap removed so chumsky's
     expected-set surfaces the constituent options

4. Hardcoded user-facing strings migrated to catalog:
   - 4 parser custom errors (incl. the known "tables need at
     least one column" wart)
   - UnknownType Display now via parse.custom.unknown_type
   - UI panel titles + mode labels (Output / Hint / SIMPLE /
     ADVANCED / Advanced:)
   - app.rs cascade rendering (action labels + summary)
   - runtime --resume CLI stderr
   - db.rs change-column diagnostic tables (7 headers + 3
     wrapper summaries + force-conversion hint)

Tests: 765 → 769 passing, 0 failed, 1 ignored (same doctest
as before). Clippy clean with -D warnings.

Deferred:
- ~25 thiserror #[error] attributes still hand-rolled
  (DbError, ArgsError, ArchiveError, PersistenceError,
  LockError). Tracked separately.
- DSL/SQL relationship in advanced mode — clarified
  implicitly via parse-first dispatch; broader ADR
  amendment to follow.
- Post-complete-parse completion gap (e.g. `save ` Tab
  can't offer `as` because `save` parses bare; same shape
  as `--create-fk` after a complete `add relationship`).

src/ui.rs

@@ -444,7 +444,7 @@ fn render_output_panel(app: &mut App, theme: &Theme, frame: &mut Frame<'_>, area
         .border_type(BorderType::Rounded)
         .border_style(Style::default().fg(theme.border))
         .title(Span::styled(
-            " Output ",
+            format!(" {} ", crate::t!("panel.output_title")),
             Style::default()
                 .fg(theme.fg)
                 .add_modifier(Modifier::BOLD),
@@ -576,15 +576,23 @@ fn render_output_line<'a>(line: &'a OutputLine, theme: &Theme) -> Line<'a> {
 fn render_input_panel(app: &App, theme: &Theme, frame: &mut Frame<'_>, area: Rect) {
     let effective = app.effective_mode();
     let (border_color, mode_color, label) = match effective {
-        EffectiveMode::Simple => (theme.border, theme.mode_simple, "SIMPLE"),
-        EffectiveMode::AdvancedPersistent => {
-            (theme.border_advanced, theme.mode_advanced, "ADVANCED")
-        }
+        EffectiveMode::Simple => (
+            theme.border,
+            theme.mode_simple,
+            crate::t!("mode.label_simple"),
+        ),
+        EffectiveMode::AdvancedPersistent => (
+            theme.border_advanced,
+            theme.mode_advanced,
+            crate::t!("mode.label_advanced"),
+        ),
         // Mixed-case label distinguishes the one-shot (`:`-triggered)
         // state from a persistent advanced mode at a glance.
-        EffectiveMode::AdvancedOneShot => {
-            (theme.border_advanced, theme.mode_advanced, "Advanced:")
-        }
+        EffectiveMode::AdvancedOneShot => (
+            theme.border_advanced,
+            theme.mode_advanced,
+            crate::t!("mode.label_advanced_one_shot"),
+        ),
     };
 
     let title = Line::from(vec![
@@ -681,7 +689,7 @@ fn render_hint_panel(app: &App, theme: &Theme, frame: &mut Frame<'_>, area: Rect
         .border_type(BorderType::Rounded)
         .border_style(Style::default().fg(theme.border))
         .title(Span::styled(
-            " Hint ",
+            format!(" {} ", crate::t!("panel.hint_title")),
             Style::default()
                 .fg(theme.fg)
                 .add_modifier(Modifier::BOLD),
@@ -757,6 +765,7 @@ fn render_candidate_line(
         let base_fg = match items[i].kind {
             crate::completion::CandidateKind::Keyword => theme.tok_keyword,
             crate::completion::CandidateKind::Identifier => theme.tok_identifier,
+            crate::completion::CandidateKind::Flag => theme.tok_flag,
         };
         let mut s = Style::default().fg(base_fg);
         if Some(i) == selected {