chore(api): add class-level @SInCE to public entry points + coverage guard (H1) (#89)

Wires up Track H1 from the v1.6.5→1.7 readiness taskboard. 26 public
types in the canonical user-reached packages now carry class-level
@SInCE 1.0.0 Javadoc tags so callers see the introduction version at
IDE quick-doc / generated Javadoc time without trawling CHANGELOG
history.

Files updated (class-level @SInCE 1.0.0):

  com.demcha.compose.GraphCompose
  com.demcha.compose.document.api.DocumentSession
  com.demcha.compose.document.api.DocumentPageSize
  com.demcha.compose.document.api.PageBackgroundFill
  com.demcha.compose.document.dsl.DocumentDsl
  com.demcha.compose.document.dsl.RichText
  com.demcha.compose.document.dsl.Transformable
  com.demcha.compose.document.dsl.{19 *Builder.java}

Baseline @SInCE 1.0.0 is the pragmatic choice: these are foundational
types that have shipped since the first GraphCompose release and
predate the CHANGELOG history that could pin a more specific version.
New public types added in subsequent PRs should use the upcoming
release version (e.g. @SInCE 1.6.6).

New guard: PublicApiSinceTagCoverageTest source-scans the three
entry-point roots (GraphCompose.java, document.api/, document.dsl/)
and fails the build if a new public top-level type lands without a
class-level @SInCE tag. internal/ sub-packages are excluded by
convention — InternalAnnotationCoverageTest covers those.

Method-level @SInCE backfill for the ~380 public methods in these
packages is intentionally out of scope; method @SInCE is now policy
for ALL new public methods (the senior-review skill enforces this on
new code) but retrofitting the existing surface is its own task.

Verification:
- ./mvnw -B -ntp test -pl . -Dtest=PublicApiSinceTagCoverageTest
  -> 1 test, 0 failures (guard green against current state)
- ./mvnw -B -ntp test -pl .
  -> full suite green, no regression from the bulk Javadoc edits

CHANGELOG entry added to v1.6.6 — Planned ### Build section.

Author: DemchaAV

CHANGELOG.md

@@ -21,6 +21,19 @@ JitPack continue to resolve through the existing coordinates.
   `./mvnw -DskipTests -P japicmp verify -pl .`; HTML/MD/XML reports
   land in `target/japicmp/`. JitPack repository is scoped to the
   `japicmp` profile, so downstream consumers do not inherit it.
+- **Class-level `@since 1.0.0` Javadoc on the public entry-point
+  surface** (Track H1). 26 public types in the canonical user-reached
+  packages (`com.demcha.compose.GraphCompose`, `com.demcha.compose.document.api.{DocumentSession, DocumentPageSize, PageBackgroundFill}`,
+  `com.demcha.compose.document.dsl.{DocumentDsl, RichText, Transformable}` plus all 19 DSL builders)
+  now carry class-level `@since 1.0.0` Javadoc tags so callers can see
+  the introduction version at IDE quick-doc / generated Javadoc time
+  without trawling CHANGELOG history. New guard test
+  `PublicApiSinceTagCoverageTest` source-scans the three entry-point
+  roots and fails the build if a new public top-level type lands
+  without a class-level `@since` tag; `internal/` sub-packages are
+  excluded by convention (`InternalAnnotationCoverageTest` covers those).
+  Method-level `@since` backfill for the ~380 public methods in these
+  packages is intentionally out of scope here and tracked separately.
 
 ### Engine internals (no behaviour change)
 

src/main/java/com/demcha/compose/GraphCompose.java

@@ -31,6 +31,7 @@
  * </ol>
  *
  * @author Artem Demchyshyn
+ * @since 1.0.0
  *
  * <h3>Build a PDF file with the canonical DSL</h3>
  * <pre>

src/main/java/com/demcha/compose/document/api/DocumentPageSize.java

@@ -8,6 +8,7 @@
  *
  * @param width page width in points
  * @param height page height in points
+ * @since 1.0.0
  */
 public record DocumentPageSize(double width, double height) {
     /**

src/main/java/com/demcha/compose/document/api/DocumentSession.java

@@ -59,6 +59,7 @@
  * <p><b>Thread-safety:</b> this type is mutable and not thread-safe.</p>
  *
  * @author Artem Demchyshyn
+ * @since 1.0.0
  */
 public final class DocumentSession implements AutoCloseable {
     private static final Logger LIFECYCLE_LOG = LoggerFactory.getLogger("com.demcha.compose.document.lifecycle");

src/main/java/com/demcha/compose/document/api/PageBackgroundFill.java

@@ -44,6 +44,7 @@
  *                    Keep {@code yRatio + heightRatio <= 1.0} so the fill
  *                    stays within the page.
  * @param color       fill color (required)
+ * @since 1.0.0
  */
 public record PageBackgroundFill(double xRatio,
                                  double yRatio,

src/main/java/com/demcha/compose/document/dsl/AbstractFlowBuilder.java

@@ -23,6 +23,7 @@
  *
  * @param <T> concrete builder type
  * @param <N> concrete node type
+ * @since 1.0.0
  */
 public abstract class AbstractFlowBuilder<T extends AbstractFlowBuilder<T, N>, N extends DocumentNode> {
     private String name = "";

src/main/java/com/demcha/compose/document/dsl/BarcodeBuilder.java

@@ -42,6 +42,7 @@
 
 /**
  * Builder for semantic barcode and QR-code nodes.
+ * @since 1.0.0
  */
 public final class BarcodeBuilder implements Transformable<BarcodeBuilder> {
     private String name = "";

src/main/java/com/demcha/compose/document/dsl/CanvasLayerBuilder.java

@@ -20,6 +20,7 @@
  * positive {@code y} is down.</p>
  *
  * @author Artem Demchyshyn
+ * @since 1.0.0
  */
 public final class CanvasLayerBuilder {
 

src/main/java/com/demcha/compose/document/dsl/DividerBuilder.java

@@ -41,6 +41,7 @@
 
 /**
  * Builder for thin horizontal divider nodes.
+ * @since 1.0.0
  */
 public final class DividerBuilder extends ShapeBuilder {
     DividerBuilder() {

src/main/java/com/demcha/compose/document/dsl/DocumentDsl.java

@@ -24,6 +24,7 @@
  * }</pre>
  *
  * @author Artem Demchyshyn
+ * @since 1.0.0
  */
 public final class DocumentDsl {
     private final DocumentSession session;