Fix print completion flow for PT-P710BT and PT-P900W.

Align raster protocol bytes and print-end sequencing by printer family, add safer status polling/retry behavior, and document the changes with regression coverage to prevent protocol regressions.

Made-with: Cursor

CHANGELOG.md

@@ -0,0 +1,19 @@
+# Changelog
+
+## Unreleased
+
+- Fix PT-P710BT/PT-P900W print completion flow and protocol bytes.
+  - Correct `G` raster transfer header length (`n1/n2`) from per-model payload size.
+  - Fix `ESC i z` page index (`n9`) and adjust print-information flags/media kind handling.
+  - Keep `ESC i A` disabled on 128-dot family and split `ESC i K` by head width.
+  - Use `0x0C -> 0x1A` end sequence on 560-dot family to complete feed/cut reliably.
+- Improve status handling around print completion.
+  - Retry status reads with backoff and safer command ordering.
+  - Add verbose post-print short polling until print-end status is observed.
+  - Add small wait before `--status` command retrieval.
+- Add protocol regression safeguards.
+  - Introduce `libptouch_protocol` helpers for shared command-byte generation.
+  - Add `protocol_regression_test` and wire it into CTest.
+- Update documentation.
+  - Add `ctest` step to build instructions.
+  - Link to changelog from README.