Create migration guides for v5

[samdenty]

Tasks

• add PR urls chore(changesets): add PR urls #6179
• Identify all breaking changes chore: filter only majors #6181
• Identify changes that can be grouped (combine multiple .changeset/*.md files into one) https://github.com/vercel/ai/pull/6206/files
• Identify changes that are bigger with more to go wrong from the small-easy-ones
• Prepare change notes for every breaking change
• Create a migration.mdx file that combines all breaking change notes, it should become part of the docs like https://ai-sdk.dev/docs/migration-guides/migration-guide-4-2

Identify and describe breaking changes

Go through every .changeset/*.md file in the v5 branch.

1. For each file that has a breaking change, use the major keyword. Otherwise use patch keyword
2. Add end-user documentation for each change. Example: docs(migration): Language Model settings have been converted to providerOptions #6175

Larger more involved changes:

• .changeset/calm-boats-complain.md

Renames / non-removals:

• .changeset/afraid-moles-cross.md The ai/rsc package has been moved separately to @ai-sdk/rsc. #6208
• .changeset/beige-socks-stare.md The generateText steps return field .reasoning has been renamed to .reasoningText #6211

Smaller changes:

• .changeset/cool-shrimps-kick.md Removed deprecated CoreToolCall and CoreToolResult types #6215
• .changeset/dull-candles-trade.md docs (openai-compatible): removed simulateStreaming from @ai-sdk/openai in favour of using middleware instead #6216
• .changeset/hungry-hotels-hunt.md embedMany now makes parallel requests, with a configurable maxParallelCalls option #6217
• .changeset/hip-eagles-attend.md Renamed Message to UIMessage #6218
• .changeset/hungry-zebras-applaud.md experimental_wrapLanguageModel is not experimental anymore #6220
• .changeset/heavy-pens-destroy.md Embedding Model V2 #6239
• .changeset/chilled-queens-remember.md Language Model V2 #6240
• .changeset/cuddly-icons-kick.md PR had no changes: chore: AI SDK 5 canary start #5534
• .changeset/cuddly-kangaroos-double.md Updated Bedrock provider to use camelCase for providerOptions #6286
• .changeset/curvy-lobsters-share.md The data UIMessage role has been removed #6287
• .changeset/eight-emus-push.md
• .changeset/famous-fans-provide.md LlamaIndexAdapter has been extracted to a separate package @ai-sdk/llamaindex #6288
• .changeset/forty-kangaroos-pull.md onCompletion has been removed in favour of onFinal #6289
• .changeset/funny-mayflies-yawn.md useChat keepLastMessageOnError option has been removed #6290
• .changeset/green-deers-scream.md
• .changeset/hungry-pets-hear.md Message mimeType has been renamed to mediaType #6291
• .changeset/itchy-bats-breathe.md
• .changeset/itchy-cars-relax.md
• .changeset/itchy-deers-jog.md logprobs has been removed from core, in favour of provider-specific logprobs implementations #6292
• .changeset/khaki-bears-drop.md structuredOutputs is now enabled by default in @ai-sdk/openai #6293
• .changeset/lemon-actors-invite.md
• .changeset/metal-insects-tease.md
• .changeset/nasty-trains-beg.md
• .changeset/neat-pillows-occur.md
• .changeset/nice-tips-walk.md
• .changeset/nine-jars-hammer.md
• .changeset/old-moons-kiss.md
• .changeset/olive-ducks-carry.md
• .changeset/pink-mangos-tickle.md
• .changeset/plenty-bears-run.md
• .changeset/poor-kids-lick.md
• .changeset/pretty-jars-reflect.md
• .changeset/proud-cows-bathe.md
• .changeset/purple-rocks-cover.md
• .changeset/quick-toys-help.md
• .changeset/rotten-peaches-doubt.md
• .changeset/rotten-walls-provide.md
• .changeset/selfish-rice-own.md
• .changeset/serious-taxis-invent.md
• .changeset/seven-pens-itch.md
• .changeset/silver-vans-march.md
• .changeset/spicy-mangos-brush.md
• .changeset/spotty-swans-know.md
• .changeset/swift-geckos-joke.md
• .changeset/tender-comics-rescue.md
• .changeset/thick-chairs-remain.md
• .changeset/thin-items-knock.md
• .changeset/three-pans-move.md
• .changeset/tiny-deers-kick.md
• .changeset/tough-mugs-fail.md
• .changeset/tough-suns-eat.md
• .changeset/tricky-zebras-cover.md
• .changeset/twelve-kids-travel.md
• .changeset/two-otters-divide.md
• .changeset/two-roses-think.md
• .changeset/unlucky-bobcats-wash.md
• .changeset/unlucky-kiwis-build.md
• .changeset/violet-taxis-work.md
• .changeset/wet-toys-burn.md
• .changeset/wicked-flowers-study.md
• .changeset/wild-candles-judge.md
• .changeset/witty-candles-pretend.md
• .changeset/young-dingos-march.md

Create migration.mdx file

tbd