docs: Remove test parity script and update coverage instructions

- Replaced by test coverage and the class-coverage nox session.
- Removed `scripts/check_test_parity.sh` and all references to it across
  documentation (`README.md`, `AGENTS.md`, and `TESTING_GUIDELINES.md`).
- Updated `TESTING_GUIDELINES.md` to include instructions for running
  `uvx nox -s class-coverage` to enforce minimum function-level coverage
  on key client classes (`PdfRestClient` and `AsyncPdfRestClient`).

Assisted-by: Codex

Author: datalogics-kam

AGENTS.md

@@ -19,9 +19,6 @@
 - `uv run pre-commit run --all-files` — enforce formatting and lint rules before
   pushing.
 - `uv run pytest` — execute the suite with the active interpreter.
-- `scripts/check_test_parity.sh` — run changed tests and report sync/async
-  parity gaps (accepts optional base/head refs, defaults to
-  `upstream/main..HEAD`).
 - `uv build` — produce wheels and sdists identical to the release workflow.
 - `uvx nox -s tests` — create matrix virtualenvs via nox and execute the pytest
   session.

README.md

@@ -45,9 +45,3 @@ uvx nox -s class-coverage
 
 To reuse an existing `coverage/py<version>/coverage.json` without rerunning
 tests, add `-- --no-tests` (and optional `--coverage-json path`).
-
-Check sync/async parity for changed tests (defaults to `upstream/main..HEAD`):
-
-```bash
-scripts/check_test_parity.sh
-```

TESTING_GUIDELINES.md

@@ -19,9 +19,9 @@ iteration required.
   asserting method/path/headers/body). Optional payload branches (for example,
   `pages`, `output`, `rgb_color`, and output-prefix fields) require explicit
   tests so serialization differences are caught early.
-- **Check parity regularly.** Run `scripts/check_test_parity.sh` (defaults to
-  `upstream/main..HEAD`) to spot missing sync/async counterparts, keeping
-  parameterized test IDs aligned between transports.
+- **Check client coverage regularly.** Run `uvx nox -s class-coverage` to
+  enforce minimum function-level coverage for `PdfRestClient` and
+  `AsyncPdfRestClient`.
 - **Exercise both sides of the contract.** Hermetic tests (via
   `httpx.MockTransport`) validate serialization and local validation. Live
   suites prove the server behaves the same way, including invalid literal