chore(native): sync native release b9829

[github-actions]

Automated sync from leehack/llamadart-native release b9829.

Changes:

• Updates hook/build.dart native release pins.
• Syncs headers from the matching llamadart-native release header bundle.
• Regenerates lib/src/backends/llama_cpp/bindings.dart via ffigen.
• Updates LiteRT-LM Dart runtime version and archive checksums when litert_lm_tag is not keep.
• Updates Apple SPM companion Package.swift binary target pins in packages/.
• Bumps companion package patch versions and updates their README/CHANGELOG native pin notes when SPM pins change.
• Updates current README/website native pin docs and the core changelog when the llama.cpp native pin changes.

Native version checklist:

• Confirm leehack/llamadart-native release b9829 includes the required native-assets archives.
• If LiteRT-LM sync was requested (litert_lm_tag is not keep), confirm leehack/litert-lm-native release keep includes the required runtime archives.
• Confirm matching Apple SPM pins changed under packages/ when Apple XCFramework releases changed.
• Confirm current README/website native pin docs and CHANGELOG.md describe the new default pin.
• Do not tag or publish companion/core packages from this PR. After merge, request explicit maintainer approval before pushing any package-specific companion tag or core vX.Y.Z tag.

[Copilot]

Pull request overview

This PR updates llamadart’s pinned native llama.cpp runtime from b9803 to b9829, aligning the hook pin, user-facing docs, and the Apple SwiftPM companion package pin/checksum with the new native release. It also adjusts the native sync script to optionally bump companion pub versions (opt-in) while still keeping changelog/docs aligned.

Changes:

• Bump the default llamadart-native pin to b9829 (hook + core changelog + docs).
• Update the Apple SwiftPM companion (llamadart_llama_cpp_flutter) to the new tag/checksum and record the pin change in an Unreleased entry.
• Enhance tool/native/sync_native_release_pins.py with --bump-companion-versions and doc dependency version syncing, and update unit tests accordingly.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
website/docs/platforms/support-matrix.md	Updates documented default native pin and bundle header to b9829.
website/docs/getting-started/installation.md	Updates installation guidance and examples to reference b9829.
tool/native/sync_native_release_pins.py	Adds opt-in companion version bumping, returns companion version for doc syncing, and updates companion changelog behavior when not bumping.
test/unit/tooling/sync_native_release_pins_script_test.dart	Updates expectations for default “no bump” behavior and adds regression coverage for repeated runs not duplicating entries.
README.md	Updates default native pin references and example asset names to b9829.
packages/llamadart_llama_cpp_flutter/README.md	Updates the SwiftPM pin string to b9829.
packages/llamadart_llama_cpp_flutter/darwin/llamadart_llama_cpp_flutter/Package.swift	Updates SwiftPM tag and XCFramework checksum for b9829.
packages/llamadart_llama_cpp_flutter/CHANGELOG.md	Adds an Unreleased entry recording the updated SwiftPM native pin.
hook/build.dart	Updates the hook’s pinned _llamaCppTag to b9829.
CHANGELOG.md	Adds an Unreleased entry describing the updated default native pin and related sync effects.

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