chore(main): release 0.31.0

[release-please]

🤖 I have created a release beep boop

0.31.0 (2026-07-25)

Features

• dart: export rpc exceptions (#7044) (8d98203)
• internal/librarian/php: parse and populate additional protos in add (#7002) (fc0fef2)
• internal/librarian/ruby: support additional_protos in librarian.yaml (#7018) (df3b941)
• python: read python tools from librarian.yaml config (#7019) (c9127b9)

Bug Fixes

• internal/librarian/php: install dev dependencies and create wrapper script for php generator (#6941) (a7106a6)
• internal/librarian/php: optimize generated file marker detection (#7036) (424d53b), refs #7017
• internal/librarian/php: remove php fallback generator installation (#7038) (cf36be0)
• internal/librarian/ruby: pass client library version to snippet metadata (#7026) (3a52836)
• internal/librarian/ruby: preserve existing version.rb file on regeneration (#7032) (583b27e)

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