feat: drop Python 3.9 and add Python 3.14 support across packaging, CI, and docs

[Copilot]

This aligns the SDK’s supported Python versions with current Kiota expectations by removing Python 3.9 support, setting 3.10 as the minimum, and adding Python 3.14 support. It updates packaging metadata, CI runtime coverage, publishing runtime, and user-facing support documentation consistently.

• Packaging metadata

  • Updated pyproject.toml to require Python >=3.10.
  • Removed the Programming Language :: Python :: 3.9 classifier.
  • Added the Programming Language :: Python :: 3.14 classifier.

• CI workflow runtime matrix

  • Removed Python 3.9 from .github/workflows/build.yml test matrix.
  • Expanded matrix coverage from 3.10–3.13 to 3.10–3.14.

• Publish workflow runtime

  • Updated .github/workflows/publish.yml to use Python 3.14 for package publishing.

• Documentation and environment references

  • Added explicit support statement in README.md that the SDK supports Python 3.10+.
  • Removed stale Python 3.9 devcontainer image reference from .devcontainer/devcontainer.json.
  • Updated the devcontainer target image to Python 3.14 (mcr.microsoft.com/devcontainers/python:3.14-bullseye), with 3.14-bookworm as the commented alternative.

# pyproject.toml
-requires-python = ">=3.9"
+requires-python = ">=3.10"

 classifiers = [
-  "Programming Language :: Python :: 3.9",
   "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
   "Programming Language :: Python :: 3.13",
+  "Programming Language :: Python :: 3.14",
 ]

[ramsessanchez]

@copilot add support for 3.14

[Copilot]

@copilot add support for 3.14

Added Python 3.14 support in pyproject.toml classifiers, the CI build matrix, and the publish workflow runtime in commit 2a0154d.

[ramsessanchez]

@copilot remove 3.9 from .devcontainer, also make sure target image is 3.14

[Copilot]

@copilot remove 3.9 from .devcontainer, also make sure target image is 3.14

Updated .devcontainer/devcontainer.json to target Python 3.14 (3.14-bullseye, with 3.14-bookworm commented option) and confirmed no Python 3.9 reference remains there in commit f7712fa.