Genkit JS 1.29.0-rc.0

What's Changed

• fix(genkit-tools/mcp): More descriptive errors in MCP by @ssbushi in #4233
• feat(js/plugins/anthropic): add prompt caching support by @cabljac in #4189
• fix(js/plugin/compat-oai): preserve legacy image URL handling when contentType is missing by @7hokerz in #4209
• feat(cli): add streaming and reasoning to dev:test-model cmd by @hugoaguirre in #4235
• fix(js/plugin/compat-oai): Fix type overload shadowing bug for OpenAI models with specific suffixes by @7hokerz in #4263
• chore(mcp): update README for AGY by @ssbushi in #4307
• feat(js/plugins/compat-oai): generalize STT module naming and add gpt-4o-mini-transcribe by @7hokerz in #4280
• chore(genkit-tools/init-ai): Update usage guides to gemini3 by @ssbushi in #4231
• feat(genkit-tools/cli): Add docs discovery tools to the CLI by @ssbushi in #4453
• feat(js/genkit): Added cancelOperation for backgroundModels by @ifielker in #4559

New Contributors

• @7hokerz made their first contribution in #4209
• @traut made their first contribution in #4329

Full Changelog: v1.28.0...v1.29.0-rc.0