feat(hint): H2 Phase C batch 1 — app-command tier-3 hints (ADR-0053)

Per-form hints for the 14 app-lifecycle commands (quit/help/hint/
rebuild/save/new/load/export/import/mode/messages/undo/redo/copy),
reference-leaning what/example with concept where it teaches (rebuild,
mode, messages, undo, export, help). hint_ids wired, catalogue + keys.rs
registered. +1 spot test; 2489 pass / 1 ignored, clippy clean.

src/app.rs

@@ -5849,6 +5849,19 @@ mod tests {
         );
     }
 
+    // ── Phase C batch 1: app-command hints render ───────────────
+
+    #[test]
+    fn f1_on_an_app_command_renders_its_hint_block() {
+        let mut app = App::new();
+        type_str(&mut app, "mode advanced");
+        f1(&mut app);
+        assert!(
+            output_contains(&app, "Switch between simple mode"),
+            "expected the `mode` tier-3 block"
+        );
+    }
+
     #[test]
     fn messages_command_toggles_verbosity_and_reports() {
         let mut app = App::new();

src/dsl/grammar/app.rs

@@ -266,7 +266,7 @@ pub static QUIT: CommandNode = CommandNode {
     shape: EMPTY_SEQ,
     ast_builder: build_quit,
     help_id: Some("app.quit"),
-    hint_ids: &[],
+    hint_ids: &["quit"],
     usage_ids: &["parse.usage.quit"],};
 
 pub static HELP: CommandNode = CommandNode {
@@ -274,7 +274,7 @@ pub static HELP: CommandNode = CommandNode {
     shape: HELP_TOPIC_OPT,
     ast_builder: build_help,
     help_id: Some("app.help"),
-    hint_ids: &[],
+    hint_ids: &["help"],
     usage_ids: &["parse.usage.help"],};
 
 pub static HINT: CommandNode = CommandNode {
@@ -283,7 +283,7 @@ pub static HINT: CommandNode = CommandNode {
     ast_builder: build_hint,
     help_id: Some("app.hint"),
     // hint_id assigned in Phase C with the tier-3 corpus (ADR-0053).
-    hint_ids: &[],
+    hint_ids: &["hint"],
     usage_ids: &["parse.usage.hint"],};
 
 pub static REBUILD: CommandNode = CommandNode {
@@ -291,7 +291,7 @@ pub static REBUILD: CommandNode = CommandNode {
     shape: EMPTY_SEQ,
     ast_builder: build_rebuild,
     help_id: Some("app.rebuild"),
-    hint_ids: &[],
+    hint_ids: &["rebuild"],
     usage_ids: &["parse.usage.rebuild"],};
 
 pub static SAVE: CommandNode = CommandNode {
@@ -299,7 +299,7 @@ pub static SAVE: CommandNode = CommandNode {
     shape: SAVE_AS_OPT,
     ast_builder: build_save,
     help_id: Some("app.save"),
-    hint_ids: &[],
+    hint_ids: &["save"],
     usage_ids: &["parse.usage.save"],};
 
 pub static NEW: CommandNode = CommandNode {
@@ -307,7 +307,7 @@ pub static NEW: CommandNode = CommandNode {
     shape: EMPTY_SEQ,
     ast_builder: build_new,
     help_id: Some("app.new"),
-    hint_ids: &[],
+    hint_ids: &["new"],
     usage_ids: &["parse.usage.new"],};
 
 pub static LOAD: CommandNode = CommandNode {
@@ -315,7 +315,7 @@ pub static LOAD: CommandNode = CommandNode {
     shape: EMPTY_SEQ,
     ast_builder: build_load,
     help_id: Some("app.load"),
-    hint_ids: &[],
+    hint_ids: &["load"],
     usage_ids: &["parse.usage.load"],};
 
 pub static EXPORT: CommandNode = CommandNode {
@@ -323,7 +323,7 @@ pub static EXPORT: CommandNode = CommandNode {
     shape: EXPORT_PATH_OPT,
     ast_builder: build_export,
     help_id: Some("app.export"),
-    hint_ids: &[],
+    hint_ids: &["export"],
     usage_ids: &["parse.usage.export"],};
 
 pub static IMPORT: CommandNode = CommandNode {
@@ -331,7 +331,7 @@ pub static IMPORT: CommandNode = CommandNode {
     shape: IMPORT_BODY_OPT,
     ast_builder: build_import,
     help_id: Some("app.import"),
-    hint_ids: &[],
+    hint_ids: &["import"],
     usage_ids: &["parse.usage.import"],};
 
 pub static MODE: CommandNode = CommandNode {
@@ -339,7 +339,7 @@ pub static MODE: CommandNode = CommandNode {
     shape: MODE_VALUE,
     ast_builder: build_mode,
     help_id: Some("app.mode"),
-    hint_ids: &[],
+    hint_ids: &["mode"],
     usage_ids: &["parse.usage.mode"],};
 
 pub static MESSAGES: CommandNode = CommandNode {
@@ -347,7 +347,7 @@ pub static MESSAGES: CommandNode = CommandNode {
     shape: MESSAGES_VALUE_OPT,
     ast_builder: build_messages,
     help_id: Some("app.messages"),
-    hint_ids: &[],
+    hint_ids: &["messages"],
     usage_ids: &["parse.usage.messages"],};
 
 pub static UNDO: CommandNode = CommandNode {
@@ -355,7 +355,7 @@ pub static UNDO: CommandNode = CommandNode {
     shape: EMPTY_SEQ,
     ast_builder: build_undo,
     help_id: Some("app.undo"),
-    hint_ids: &[],
+    hint_ids: &["undo"],
     usage_ids: &["parse.usage.undo"],};
 
 pub static REDO: CommandNode = CommandNode {
@@ -363,7 +363,7 @@ pub static REDO: CommandNode = CommandNode {
     shape: EMPTY_SEQ,
     ast_builder: build_redo,
     help_id: Some("app.redo"),
-    hint_ids: &[],
+    hint_ids: &["redo"],
     usage_ids: &["parse.usage.redo"],};
 
 pub static COPY: CommandNode = CommandNode {
@@ -371,5 +371,5 @@ pub static COPY: CommandNode = CommandNode {
     shape: COPY_VALUE_OPT,
     ast_builder: build_copy,
     help_id: Some("app.copy"),
-    hint_ids: &[],
+    hint_ids: &["copy"],
     usage_ids: &["parse.usage.copy"],};

src/friendly/keys.rs

@@ -234,6 +234,41 @@ pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     ("hint.err.foreign_key.child_side.what", &[]),
     ("hint.err.foreign_key.child_side.example", &[]),
     ("hint.err.foreign_key.child_side.concept", &[]),
+    // Phase C batch 1 — app-lifecycle command hints.
+    ("hint.cmd.quit.what", &[]),
+    ("hint.cmd.quit.example", &[]),
+    ("hint.cmd.help.what", &[]),
+    ("hint.cmd.help.example", &[]),
+    ("hint.cmd.help.concept", &[]),
+    ("hint.cmd.hint.what", &[]),
+    ("hint.cmd.hint.example", &[]),
+    ("hint.cmd.rebuild.what", &[]),
+    ("hint.cmd.rebuild.example", &[]),
+    ("hint.cmd.rebuild.concept", &[]),
+    ("hint.cmd.save.what", &[]),
+    ("hint.cmd.save.example", &[]),
+    ("hint.cmd.new.what", &[]),
+    ("hint.cmd.new.example", &[]),
+    ("hint.cmd.load.what", &[]),
+    ("hint.cmd.load.example", &[]),
+    ("hint.cmd.export.what", &[]),
+    ("hint.cmd.export.example", &[]),
+    ("hint.cmd.export.concept", &[]),
+    ("hint.cmd.import.what", &[]),
+    ("hint.cmd.import.example", &[]),
+    ("hint.cmd.mode.what", &[]),
+    ("hint.cmd.mode.example", &[]),
+    ("hint.cmd.mode.concept", &[]),
+    ("hint.cmd.messages.what", &[]),
+    ("hint.cmd.messages.example", &[]),
+    ("hint.cmd.messages.concept", &[]),
+    ("hint.cmd.undo.what", &[]),
+    ("hint.cmd.undo.example", &[]),
+    ("hint.cmd.undo.concept", &[]),
+    ("hint.cmd.redo.what", &[]),
+    ("hint.cmd.redo.example", &[]),
+    ("hint.cmd.copy.what", &[]),
+    ("hint.cmd.copy.example", &[]),
     (
         "hint.ambient_invalid_ident",
         &["kind", "found"],

src/friendly/strings/en-US.yaml

@@ -406,6 +406,56 @@ hint:
       what: "Link two tables so a parent row can own many child rows."
       example: "add 1:n relationship from Customers.id to Orders.customer_id"
       concept: "The \"1:n\" means one parent, many children. The child column holds the foreign key; add `--create-fk` to create that column if it doesn't exist yet."
+    # App-lifecycle commands (Phase C batch 1). Reference-leaning, so
+    # `concept` appears only where there's a real idea to teach.
+    quit:
+      what: "Leave the playground. Your project is already saved to disk."
+      example: "quit"
+    help:
+      what: "List every command, or show the detail for one."
+      example: "help insert"
+      concept: "`help` is the reference; press F1 while typing for a hint about the command you're building right now."
+    hint:
+      what: "Explain the most recent error — or, pressing F1 while typing, the command you're building."
+      example: "hint"
+    rebuild:
+      what: "Rebuild the project database from its saved text files."
+      example: "rebuild"
+      concept: "The text files (project.yaml + the data folder) are the source of truth; the database is derived and can always be rebuilt from them."
+    save:
+      what: "Save the current project under a name; `save as` copies it to a new one."
+      example: "save as my-shop"
+    new:
+      what: "Close the current project and start a fresh temporary one."
+      example: "new"
+    load:
+      what: "Open the project picker to switch to a saved project."
+      example: "load"
+    export:
+      what: "Write a shareable zip of the project — its text files only, never the database."
+      example: "export my-shop.zip"
+      concept: "The zip carries the schema and data as text, so anyone can rebuild the very same database from it."
+    import:
+      what: "Unpack a project zip into a new project and switch to it."
+      example: "import my-shop.zip as shop-copy"
+    mode:
+      what: "Switch between simple mode (the guided teaching commands) and advanced mode (raw SQL)."
+      example: "mode advanced"
+      concept: "Simple mode uses keyword commands; advanced mode lets you write SQL directly. A leading `:` runs a single advanced command without switching modes."
+    messages:
+      what: "Show or set how much detail error messages give."
+      example: "messages short"
+      concept: "Verbose (the default) adds a fix-it hint under each error headline; short shows just the headline."
+    undo:
+      what: "Undo the most recent change, after a confirmation."
+      example: "undo"
+      concept: "Every data or schema change is snapshotted first, so you can step back; `redo` re-applies what you undid."
+    redo:
+      what: "Re-apply the most recently undone change."
+      example: "redo"
+    copy:
+      what: "Copy the output panel to the clipboard — all of it, or just the last command's output."
+      example: "copy last"
   err:
     foreign_key:
       child_side: