Drop EOL Python 3.9, bump pddl-examples, retire Mergify

- Python 3.9 reached end of life in October 2025: the test matrix now
  runs 3.10-3.14 and requires-python moves to >=3.10 to match.
- pddl-examples submodule advances to today's synced main (d2de477),
  which now auto-imports from planning.domains.
- Remove .mergify.yml: the auto-merge rule needs an approving review
  that a single-maintainer org never produces, and the reviewer-assign
  rule pings an inactive account. Every recent PR was merged manually;
  the Mergify check reported neutral on all of them.

Author: guilyx

.github/workflows/tests.yml

@@ -13,7 +13,9 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13', '3.14']
+        # 3.9 reached end of life in October 2025; the floor is now 3.10
+        # (kept in sync with requires-python in pyproject.toml).
+        python-version: ['3.10', '3.11', '3.12', '3.13', '3.14']
         # The charts are an optional extra, so most of the matrix runs without
         # matplotlib — that is the configuration nearly every user installs,
         # and it proves the core stays importable without it. One entry pulls

.mergify.yml

@@ -7,7 +7,7 @@ name = "jupyddl"
 version = "2.3.0"
 description = "A pure-Python PDDL planning framework: parser, grounding, classical-to-SOTA planners, heuristics and benchmarking."
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = { text = "Apache-2.0" }
 authors = [{ name = "Erwin Lejeune" }]
 keywords = ["pddl", "planning", "heuristic-search", "a-star", "lm-cut", "automated-planning"]
@@ -20,7 +20,6 @@ classifiers = [
     "License :: OSI Approved :: Apache Software License",
     "Operating System :: OS Independent",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",