fix(config): expand ~ in blaise.cfg unit-path / rtl-src values

A blaise.cfg value like `rtl-src=~/devel/blaise/compiler/src/main/pascal` was
treated as RELATIVE (only a leading '/' counted as absolute) and prefixed with
the config directory, and the `~` was never expanded — producing a bogus path
like `/home/user/cwd/~/devel/...` and an "RTL source directory not found" error.

Resolve config paths through a shared helper: a leading '~' or '~/' expands to
$HOME (and is treated as absolute); a leading '/' is used as is; anything else
is relative to the config file's directory.  Applies to both unit-path= and
rtl-src=.  If $HOME is unset, '~' is left untouched rather than mis-resolved.

Tests: TConfigTests.TestParseTildePath_ExpandsToHome and
TestParseRtlSrcTilde_ExpandsToHome.  Verified end-to-end: a blaise.cfg using
`~/...` for unit-path + rtl-src compiles with no path flags from any CWD.

compiler/src/main/pascal/uConfig.pas

@@ -53,6 +53,36 @@ begin
   Result := '';
 end;
 
+{ Resolve a blaise.cfg path value.  An absolute path (leading '/') is used as
+  is; a leading '~' or '~/' expands to $HOME (so a config can name paths under
+  the user's home directory); anything else is relative and resolved against
+  ABaseDir (the config file's own directory). }
+function ResolveCfgPath(const AValue, ABaseDir: string): string;
+var
+  Home: string;
+begin
+  if Length(AValue) = 0 then
+    Exit('');
+  { Home expansion: '~' alone, or a '~/...' prefix. }
+  if (Copy(AValue, 0, 1) = '~') and
+     ((Length(AValue) = 1) or (Copy(AValue, 1, 1) = '/')) then
+  begin
+    Home := GetEnvironmentVariable('HOME');
+    if Home <> '' then
+    begin
+      if Length(AValue) = 1 then
+        Exit(Home);
+      { drop the '~', keep the rest (which starts with '/') }
+      Exit(IncludeTrailingPathDelimiter(Home) + Copy(AValue, 2, Length(AValue)));
+    end;
+    { No $HOME — leave '~' untouched rather than mis-resolving. }
+    Exit(AValue);
+  end;
+  if Copy(AValue, 0, 1) = '/' then
+    Exit(AValue);
+  Result := IncludeTrailingPathDelimiter(ABaseDir) + AValue;
+end;
+
 procedure ParseConfigLines(ALines: TStringList; const ABaseDir: string;
   APaths: TStringList; var ARtlSrc: string);
 var
@@ -75,17 +105,9 @@ begin
     Key   := Trim(Copy(Line, 0, EqPos));
     Value := Trim(Copy(Line, EqPos + 1, Length(Line)));
     if SameText(Key, 'unit-path') then
-    begin
-      if (Length(Value) > 0) and (Copy(Value, 0, 1) <> '/') then
-        Value := IncludeTrailingPathDelimiter(ABaseDir) + Value;
-      APaths.Add(Value);
-    end
+      APaths.Add(ResolveCfgPath(Value, ABaseDir))
     else if SameText(Key, 'rtl-src') then
-    begin
-      if (Length(Value) > 0) and (Copy(Value, 0, 1) <> '/') then
-        Value := IncludeTrailingPathDelimiter(ABaseDir) + Value;
-      ARtlSrc := Value;
-    end
+      ARtlSrc := ResolveCfgPath(Value, ABaseDir)
     else
       ; { silently skip unrecognised keys }
   end;

compiler/src/test/pascal/cp.test.config.pas

@@ -31,6 +31,8 @@ type
     procedure TestParseRtlSrc_Absolute_SetsValue;
     procedure TestParseRtlSrc_Relative_ResolvedAgainstBaseDir;
     procedure TestParseRtlSrc_Absent_LeavesSeedUnchanged;
+    procedure TestParseTildePath_ExpandsToHome;
+    procedure TestParseRtlSrcTilde_ExpandsToHome;
     procedure TestFindConfigFile_NextToBinary;
   end;
 
@@ -289,6 +291,51 @@ begin
   end;
 end;
 
+procedure TConfigTests.TestParseTildePath_ExpandsToHome;
+var
+  Lines, Paths: TStringList;
+  Home: string;
+begin
+  Home := GetEnvironmentVariable('HOME');
+  if Home = '' then begin Ignore('no $HOME'); Exit end;
+  Lines := TStringList.Create();
+  Paths := TStringList.Create();
+  try
+    { A '~/...' unit-path expands to $HOME/..., NOT resolved against the base. }
+    Lines.Add('unit-path=~/devel/blaise/runtime');
+    ParseConfigLines(Lines, '/some/base', Paths);
+    AssertEquals('one path', 1, Paths.Count);
+    AssertEquals('~ expanded to $HOME',
+      IncludeTrailingPathDelimiter(Home) + 'devel/blaise/runtime',
+      Paths.Strings[0]);
+  finally
+    Lines.Free();
+    Paths.Free();
+  end;
+end;
+
+procedure TConfigTests.TestParseRtlSrcTilde_ExpandsToHome;
+var
+  Lines, Paths: TStringList;
+  Rtl, Home: string;
+begin
+  Home := GetEnvironmentVariable('HOME');
+  if Home = '' then begin Ignore('no $HOME'); Exit end;
+  Lines := TStringList.Create();
+  Paths := TStringList.Create();
+  try
+    Rtl := '';
+    Lines.Add('rtl-src=~/devel/blaise/compiler/src/main/pascal');
+    ParseConfigLines(Lines, '/some/base', Paths, Rtl);
+    AssertEquals('~ in rtl-src expanded to $HOME',
+      IncludeTrailingPathDelimiter(Home) + 'devel/blaise/compiler/src/main/pascal',
+      Rtl);
+  finally
+    Lines.Free();
+    Paths.Free();
+  end;
+end;
+
 procedure TConfigTests.TestFindConfigFile_NextToBinary;
 var
   CfgPath: string;