Add DEPRECATIONS.md (initial)

Author: steinkel

DEPRECATIONS.md

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+# Deprecation scan: WIP
+
+This file is a living record of the deprecation warnings discovered while running the test suite and the corrective actions taken.
+
+Status: scan not yet run on CI from this environment. I will run vendor/bin/phpunit locally/CI and update this file with full deprecation messages and locations.
+
+Planned steps
+
+1. Run vendor/bin/phpunit and capture all deprecation notices (message, file, line).
+2. Update tests to replace deprecated PHPUnit APIs (assertInternalType -> assertIs*, setUp/tearDown signatures to return void, remove @expectedException annotations, update assertAttribute* usages, etc.).
+3. Update source code to replace deprecated CakePHP APIs flagged by tests.
+4. Update fixtures/bootstrap to avoid deprecated calls.
+5. Re-run test suite until deprecation-free.
+6. Add the full before/after test output to the PR description.
+
+Notes
+- Minimal, non-breaking changes will be preferred. Any deprecation that requires a breaking change will be documented and left for a major-version work item.
+- Branch: copilot/update-deprecated-code-phpunit
+
+Updates will be appended here as they are discovered and fixed.
+
+
+Initial entries
+
+- None yet (scan pending)