Phase 1 vollstaendig abgeschlossen; neue Vorgaben verankert

Frontend-Vervollstaendigung (keine offenen Punkte mehr in Phase 1):
- MID$-Anweisung, DEF-FN-Blockform, COMMON/SHARED/STATIC,
  LPRINT, VIEW PRINT, NAME AS, LOCK/UNLOCK, Ereignissteuerung
  (TIMER/KEY(n)/UEVENT ON|OFF|STOP), Metabefehle $INCLUDE/$STATIC/$DYNAMIC
- Komplette Datei-E/A-Grammatik: OPEN (beide Syntaxen, inkl. ISAM- und
  ACCESS/LOCK-Klauseln), CLOSE, FIELD, GET/PUT, LSET/RSET, WRITE, SEEK
- Semantik: UDT-Feldtypen, SHARED-Import von Modulvariablen,
  Konstantenfaltung (Invalid constant), OPTION BASE erfasst
- Non-Features konsistent zur Compile-Zeit abgewiesen: Hardware-Naehe,
  CHAIN, Grafik-Anweisungen, SOUND/PLAY ("Feature unavailable")
- 33 Frontend-Tests, Korpus-Meilenstein weiter gruen

Neue Vorgaben:
- Stufe-2-Ideen: SQLite/Embedded-SQL mit Record-Buffern; Runtime-
  Bibliotheken (z.B. crossterm) als BASIC-Bibliotheken
- Erster Kompatibilitaetstest: github.com/cout/vbdos (extern, wird nicht
  einvendort); binaer-.FRM-Konverter als Phase-4-Aufgabe (tbc convert-frm)
- Doku als Definition of Done: docs/ = Ist-Dokumentation, IDE-Hilfe
  rendert Markdown dynamisch zur Fenstergroesse (Phase-5-Aufgabe)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/tb-frontend/src/ast.rs

@@ -96,7 +96,7 @@ pub struct CaseArm {
 pub struct VarDecl {
     pub name: String,
     pub suffix: Option<Suffix>,
-    /// `None` = Skalar; sonst Dimensionen `(untergrenze TO obergrenze)`.
+    /// `None` = Skalar; leerer Vec = Array ohne Dimensionsangabe (`a()`).
     pub dims: Option<Vec<(Option<Expr>, Expr)>>,
     pub as_type: Option<TypeName>,
     pub pos: SourcePos,
@@ -161,12 +161,47 @@ pub struct Proc {
     pub pos: SourcePos,
 }
 
+/// `OPEN … FOR modus`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum OpenMode {
+    Input,
+    Output,
+    Append,
+    Random,
+    Binary,
+    Isam,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum AccessMode {
+    Read,
+    Write,
+    ReadWrite,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum LockClause {
+    Shared,
+    LockRead,
+    LockWrite,
+    LockReadWrite,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum EventAction {
+    On,
+    Off,
+    Stop,
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub enum Stmt {
     Label(String),
     LineNumber(u32),
     Assign { target: Expr, value: Expr, pos: SourcePos },
     Print {
+        /// LPRINT (Druckerausgabe) statt PRINT.
+        printer: bool,
         file: Option<Expr>,
         using: Option<Expr>,
         items: Vec<PrintItem>,
@@ -212,6 +247,17 @@ pub enum Stmt {
     System,
     Exit { kind: ExitKind, pos: SourcePos },
     Dim { shared: bool, redim: bool, decls: Vec<VarDecl>, pos: SourcePos },
+    /// `SHARED`-Anweisung in einer Prozedur (Zugriff auf Modulvariablen).
+    SharedDecl { decls: Vec<VarDecl>, pos: SourcePos },
+    /// `STATIC`-Anweisung in einer Prozedur.
+    StaticDecl { decls: Vec<VarDecl>, pos: SourcePos },
+    /// `COMMON [SHARED] [/block/] liste`.
+    CommonDecl {
+        shared: bool,
+        block: Option<String>,
+        decls: Vec<VarDecl>,
+        pos: SourcePos,
+    },
     Erase { names: Vec<Expr>, pos: SourcePos },
     ConstDecl { items: Vec<(String, Option<Suffix>, Expr)>, pos: SourcePos },
     DefType { ty: TypeName, ranges: Vec<(char, char)>, pos: SourcePos },
@@ -234,9 +280,69 @@ pub enum Stmt {
         body: Expr,
         pos: SourcePos,
     },
-    /// Geparst, aber erst in Phase 3 implementiert (Datei-E/A u. ä.);
-    /// die Tokens der Anweisung wurden übersprungen.
-    NotYetImplemented { keyword: String, pos: SourcePos },
+    /// Blockform `DEF FNname(...) … END DEF`.
+    DefFnBlock {
+        name: String,
+        suffix: Option<Suffix>,
+        params: Vec<Param>,
+        body: Vec<Stmt>,
+        pos: SourcePos,
+    },
+    // ---- Datei-E/A (Laufzeit in Phase 3, Grammatik vollständig) ----
+    Open {
+        file: Expr,
+        mode: Option<OpenMode>,
+        /// Bei `FOR ISAM typname tabellenname`.
+        isam: Option<(String, String)>,
+        access: Option<AccessMode>,
+        lock: Option<LockClause>,
+        number: Expr,
+        len: Option<Expr>,
+        pos: SourcePos,
+    },
+    /// Alte Syntax `OPEN modus$, [#]n, datei$ [, reclen]`.
+    OpenLegacy {
+        mode: Expr,
+        number: Expr,
+        file: Expr,
+        len: Option<Expr>,
+        pos: SourcePos,
+    },
+    CloseStmt { files: Vec<Expr>, pos: SourcePos },
+    FieldStmt { file: Expr, fields: Vec<(Expr, Expr)>, pos: SourcePos },
+    GetPut {
+        put: bool,
+        file: Expr,
+        recnum: Option<Expr>,
+        var: Option<Expr>,
+        pos: SourcePos,
+    },
+    LsetRset { rset: bool, target: Expr, value: Expr, pos: SourcePos },
+    WriteStmt { file: Option<Expr>, items: Vec<Expr>, pos: SourcePos },
+    SeekStmt { file: Expr, position: Expr, pos: SourcePos },
+    LockStmt {
+        unlock: bool,
+        file: Expr,
+        from: Option<Expr>,
+        to: Option<Expr>,
+        pos: SourcePos,
+    },
+    NameStmt { old: Expr, new: Expr, pos: SourcePos },
+    // ---- Bildschirm/Ereignisse ----
+    /// `VIEW PRINT [oben TO unten]`.
+    ViewPrint { top: Option<Expr>, bottom: Option<Expr>, pos: SourcePos },
+    /// `TIMER ON`, `KEY(5) OFF`, `UEVENT STOP` …
+    EventControl {
+        device: String,
+        index: Option<Expr>,
+        action: EventAction,
+        pos: SourcePos,
+    },
+    // ---- Metabefehle ----
+    /// `'$INCLUDE: 'datei''` — Auflösung übernimmt der Compile-Treiber.
+    Include { path: String, pos: SourcePos },
+    /// `'$STATIC` / `'$DYNAMIC`.
+    MetaArrays { static_arrays: bool, pos: SourcePos },
 }
 
 #[derive(Debug, Clone, PartialEq)]